Unleashing the Power of Light: A Comprehensive Exploration of High-Power Semiconductor Lasers and Their Evolution in the 20th Century’s Four Great Inventions

Summary

Lasers are known as "the fastest knife", "the most accurate ruler", and "the brightest light", and are known as the four new great inventions of the 20th century, along with atomic energy, computers, and semiconductors.
High-power semiconductor lasers have a wide range of applications in industrial processing, medical cosmetology, optical fiber communication, unmanned driving, intelligent robots, etc. How to do it
High-power semiconductor laser light source has always been an international research frontier and discipline hotspot. To this end, the development history of high-power semiconductor lasers is briefly described
Shi reviewed the sharing technology of high-power semiconductor lasers, including high-power chip technology and high-power beam combining technology, and developed high-power semiconductor lasers
The direction of the exhibition was prospected.

keyword：  Laser; semiconductor lasers; High-power; chip technology; Bundle closing technique

 1 Introduction

Semiconductor lasers are small in size, light in weight, and have electro-optical conversion efficiency
High rate, high reliability and long life and other advantages in industrial processing, biological
It has important applications in fields such as medical and national defense [1-10]. 1962
In the same year, American scientists successfully developed the first generation of GaAs homojunctions
Implantable semiconductor lasers [11-12]. 1963, Soviet Science
Alferov et al. [13-14] of the Institute of Physics announced the successful development of a double heterojunction semiconductor laser. After the 80s of the 20th century, due to
The theory of band engineering was introduced, and the growth of crystalline epitaxial materials emerged
New processes such as molecular beam epitaxy (MBE) and organometallic compound chemistry
Vapor deposition (MOCVD), etc.], quantum well lasers are on the dance of history
The performance of the device is greatly improved and the high power output is achieved.

High-power semiconductor lasers are mainly divided into single tube and Bar bar
kind of structure [15], the single-tube structure mostly adopts the design of wide strips and large optical cavities, and
The gain area has been increased to achieve high power output and reduce cavity surface catastrophism
Damage; The Bar bar structure is a parallel linear array of multiple single-tube lasers
Lasers work at the same time, and then achieve high power by means such as beam combining
Laser output. The first high-power semiconductor lasers were mainly used in:
Pumped solid-state lasers and fiber lasers, the wavelength band is mainly 808nm
and 980nm. With a single high-power diode laser in the near-infrared band
The maturity of metatechnology and the reduction of costs have made it possible to base on it all
The performance of solid-state lasers and fiber lasers is constantly improving, and the single tube is continuous
The wave (CW) output power was reached from 8.1W in the 90s of the 20th century
29.5W[16] level, bar CW output power reached
1010W[17] horizontal, pulse output power up to 2800W[18] water
It has greatly promoted the application process of laser technology in the field of processing.
The cost of a diode laser as a pump source accounts for the solid-state laser assembly
1/3~1/2 of this one, accounting for 1/2~2/3 of fiber lasers. therefore
Fiber lasers and all-solid-state lasers are developing rapidly, with high power semiconductors
The development of bulk lasers has contributed a lot.

With the continuous improvement of the performance of semiconductor lasers, the cost is not
The range of applications is becoming more and more extensive. How to achieve high power
Semiconductor lasers have always been the forefront and hot spot of research.
To realize high-power semiconductor laser chips, it is necessary to start from materials and junctions
The three aspects of structure and cavity surface protection are considered:
1) Materials technology. It can be possible to increase both the gain and prevent oxidation
The corresponding technologies include strain bead trap technology and aluminum-free
Quantum well technology.
2) Structural technology. In order to prevent the chip from burning at high output power
Asymmetric waveguide technology and wide waveguide large cavity technology are usually used.
3) Cavity surface protection technology. In order to prevent catastrophic optical mirror damage
COMD, the main techniques include non-absorbable cavity surface technology, cavity surface
Passivation technology and coating technology.

With the development of all walks of life, whether as a pump source, or
Direct application has put forward further demand for semiconductor laser light source
Beg. In order to maintain a high beam quality in the case of higher power requirements
quantity, it is necessary to carry out laser beam combining.
Semiconductor laser beam combining technology mainly includes: conventional beam combination
(TBC), Dense Wavelength Beam Combining (DWDM) technology, Spectral Beam Combination
(SBC) technology, coherent beam (CBC) technology, etc. This article is mainly about
The above techniques are outlined.
2. An important technical means to realize high-power lasers

2.1 Side-emitting high-power semiconductor laser chip technology
2.1.1 Materials technology
2.1.1.1 Strain subwell technology
Quantum wells are the most widely used active semiconductor lasers
zone, which exhibits a quantized sub-band and ladder state density, will
Greatly improve the threshold current density and temperature stability of the laser; open
By changing the well width and barrier height, the quantized energy can be changed
The amount of spacing realizes the tunable characteristics of the laser, which is different from the traditional double heterogeneity
Compared with semiconductor lasers, the threshold of the laser can be effectively reduced
value current, improve quantum efficiency and differential gain. And in quantum wells
The introduction of strain will significantly change its own band structure, through
Adjust the position of the heavy and light hole bands in the valence band to increase the number of off-chip
Design parameters and degrees of freedom for extended structures. In general, in III-V
Pressure is introduced into the epitaxial structure of quantum wells composed of ternary and quaternary materials
strain, which will exacerbate the change in the band function, thereby reducing the threshold of the laser
value current; And the introduction of tensile strain, it will flatten the band function, at a certain level
To a certain extent, the gain of the material in the working state at high power is improved. should
The presence of variable sub-traps makes it possible to obtain the desired energy band junction by adjusting the strain
and increased gain became possible [19-20], enabling the semiconductor laser
There's a big leap forward in performance.

In 1984, Laidig et al. [21] first reported strain-based work
InGaAs/GaAs quantum wells for lasers at higher threshold currents
A laser with a wavelength of 1 μm was obtained at a density (1.1 kA/cm2),
The threshold current density was reduced to 465 A/cm2 by refining the process [22].
In 1991 AT&TBell laboratories utilized the MBE method to lower
The threshold current ——— as low as 45A/cm2, which is basically the theoretical extreme
[23]. In July 1993, Hayakawa et al. [24] in Japan used
The GaAs/AlGaAs tension strain subwell is obtained at the output wavelength
780nm transverse magnetic (TM) mode CW laser.
2.1.1.2 Aluminum-free quantum well technology
Aluminum-free lasers have obvious advantages compared to aluminum-based lasers
Advantages:
1) Aluminum-free materials have higher COMD work than aluminum-containing materials
Rate density. The aluminum in the active zone is susceptible to oxidation and dark line defects.
As a result, the power density decreases when COMD occurs, making it easier to generate
COMD, thus limiting the power and lifetime of the laser.
2) At the same time, the electricity of aluminum-free quantum wells is relative to aluminum-containing quantum wells
The resistance is lower and the thermal conductivity is higher, so the surface recombination rate is low and the surface temperature is low
The rise and low cavity surface degradation rate is slow, which inhibits the climbing of dark line defects
and the internal degradation rate of the material is slow.

In 1998, Pendse et al. [25] in the United States initially proposed that there was none
Aluminum quantum well lasers have higher reliability. In 1999, Mawsi et al. [26] in the United States matched the InGaAsP single with the GaAs lattice
The reliability of quantum well lasers has been studied, proving that there are no aluminum devices
The temperature rise of the end face of the piece is much lower than that of an aluminum-containing AlGaAs laser, and
At an operating temperature of 10°C, a maximum output power of 3.2W is obtained
Rate. In 2008, the 13th Research Institute of China Electronics Technology Group Corporation
It is reported that the output power of the quasi-continuous array with a cavity length of 1 mm without aluminum can be reached
40W, aluminum-free 1cm long coated bar at 180A working electricity
current, the output power is greater than 185W [27]. 2013, Shandong University
It is reported that the output power of the aluminum-free active zone reaches 20A working current
20.86W laser [28].
2.1.2 Waveguide structure technology
2.1.2.1 Asymmetric waveguide technology

In the large optical cavity structure, as the size of the waveguide increases, the device's
The series resistance also increases. Therefore, in order to reduce the series resistance, it is usually necessary for p
The type restriction layer is subjected to a higher doping. Experimental studies have found that light absorption
The doping concentration is proportional to the doping region and is empty in the p-type material
The loss of photons absorbed by cavities is greater than that absorbed by electrons in n-type materials
Loss of subs [29-32]. In this way, in the symmetrical waveguide structure, the p-type is highly doped
The light absorption of the miscellaneous carriers is the formation of internal loss, resulting in the loss of efficiency
The main reason for the low. It can pass the thickness of p-type waveguides and n-type waveguides
Degree asymmetry, refractive index asymmetry and other adjustment methods, so that the light field distribution is exhausted
The amount limit expands in the n-type region, thus reducing the series resistance and guilt
to obtain high efficiency.
In 2007, the Institute of Semiconductors of the Chinese Academy of Sciences reported aluminum-free
Asymmetric waveguide structure laser in the active region, with a wavelength of 808nm, connected
Under continuous operating conditions, the output power can reach 6W [33], which was achieved in 2009
The 980nm semiconductor laser has an internal loss of only 0.78cm-1 [34],
In 2010, a 980nm semiconductor laser efficiency was achieved
58.4%[35]。 In 2013, Japan's Morita et al. [36] implemented the article
The width is 100 μm, the cavity length is 4 mm, and the CW output power is
19.8W, 68% conversion efficiency at 20°C
Utensil. In 2020, Ryvkin et al. [37] of Finland symmetrically symmetric waves
The refractive index of conduction, limiting factor, carrier concentration, internal loss, etc
The surface was simulated and analyzed, and finally the short-cavity structure was designed to calculate the CW loss
Diode lasers with a power of up to 40W.
2.1.2.2 Large cavity technology

In order to obtain high output power, it is necessary to increase the COMD threshold
Reduces the energy density of the light field in the active region and the confined layer. This needs to be increased
The large waveguide scale, increasing the size of the light spot, broadening the light field distribution, this
It is the large cavity technology. While increasing the waveguide scale, it can be optimized
The waveguide structure reduces the divergence angle of the far-field fast-axis beam of the laser.
In 2005, Knauer et al. [38] in Germany achieved 808 nm
Large cavity structure, obtained at 25°C, CW output power is 15W, the fast-axis far-field divergence angle is 18°. In 2006, Bookham designed gradient refraction using InGaAs/AlGaAs materials
The rate of the optical cavity chip is obtained at a temperature of 16 °C and a current of 20A
A CW output power greater than 17W was obtained [39]. In 2008, Xu
et al. [40] using the gradient fold of InAlGaAs/AlGaAs/GaAs materials
The new large optical cavity structure of emissivity realizes CW transmission at 25°C
A 915nm laser with a power of 23W. Germany, 2009
Crump et al. [41] used InGaAs/GaAsP materials and core diameters
The large optical cavity structure of 2.5μm obtains a CW output power of 20W 975nm single-tube diode laser with a lifetime greater than
4000h。 In 2015, Ling Xiaohan et al. [42] of Beijing University of Technology designed it
980nm large cavity single light-emitting strip high-power semiconductor laser, its
The CW output power reaches 12W, and the device synthesis is obtained by aging experiments
The synthetic product rate reached 40%. In 2019, Qiao Chuang of Changchun University of Science and Technology
et al. [43] designed and fabricated an asymmetrical large optical cavity structure, and prepared it
890nm period Distributed Bragg Mirror (DBR) grating, most
Finally, the output power is 10.7W, and the slope efficiency is 0.73W/A laser output.

2.1.3 Cavity surface technology
2.1.3.1 Non-absorbent cavity surface technology
By increasing the width of the quantum well band gap near the cavity surface, the cavity surface is made is transparent to the lasing wavelength, which is the non-absorbing cavity surface technology. Non-suction
The cavity surface reduces heat generation due to non-radiative recombination and light absorption
and the number of photogenerated carriers, which is to increase the output work of the semiconductor laser
Rate and reliability of an effective method. At present, the production of non-absorbent cavity surfaces
The methods mainly include: quadratic epitaxial growth technology and quantum well hybrid technology
Technique. Secondary epitaxial growth is a kind of wide bandgap through etching and regrowth
Semiconductor materials. This method is technically difficult, complex and difficult
The crystal quality of the binding interface is guaranteed [44]. Quantum well hybrid technology pass
Film deposition or impurity injection is carried out on the epitaxial wafer, and then passed through the high
Rapid annealing at temperature, so that the constituent elements diffuse each other, resulting in traps and barriers
The composition changes, resulting in an increase in the bandgap structure. This method works
It is relatively simple, low-cost, and effective [45], but requires high-temperature strips
Thermal annealing under the piece may cause some damage to the device.

In 1984, BT Research Laboratories utilized selective epitaxy
The growth technology prepared the AlGaAs large optical cavity laser with non-absorbing cavity surface
, the output work obtained when the pulse is output (pulse width is 100ns).
The rate is 2~3 times higher than that of ordinary lasers [46]. Kyoto, Japan, 1999
The university prepared 780nm AlGaAs/ with non-absorbing cavity surface
GaAs high-power semiconductor lasers, the maximum output power is conventional
3 times that of lasers [47]. Prepared in 2000 by the University of Glasgow, UK
GaAs/AlGaAs semiconductor laser with non-absorbing cavity surface
, the highest output power in the event of COMD is a normal laser
2 times [48]. In 2015, Hamamatsu Optoelectronics Co., Ltd. prepared
With a non-absorbing cavity surface with a bandgap difference of 100 meV, the continuous output power of the 915nm band InGaAs wide strip diode laser is 20W, reliable working time is more than 5000h, and the maximum efficiency is exceeded
65%[49]。

2.1.3.2 Cavity surface passivation technology
The natural cleavage plane of a diode laser is highly susceptible to deliquescent and oxygen
Chemical, oxide and contamination can easily become non-radiative recombination centers, thus exacerbating
The sharp rise in the cavity surface junction temperature eventually leads to COMD, which makes
Device failure. Cavity surface passivation is effective in removing semiconductor lasers
Impurities such as contamination and oxide layer on the cavity surface reduce the surface density of the cavity surface
degree, so as to effectively improve the thermal stability of the device, inhibit COMD, and most
Finally, the maximum output power is increased and the reliability of the device is improved, which is high performance
Ability and stable work to provide security.
In 1987, Sandroff et al. of Bell Communications Research [50]
Invented cavity vulcanization treatment technology. Na2 is used
S·9H2
O soluble
Liquids will be cavities for GaAs/AlGaAs heterojunction bipolar transistors (HBTs).
The surface is passivated, and the current gain of HBT after vulcanization treatment is increased by 60
Times. In 1996, Syrbu et al. [51] in the evaporation of high-reflective/anti-reflection coatings
Using in situ growth ZnSe technology, 980 nm InGaAs was semiconducted
The cavity surface of the bulk laser is passivated to increase the continuous output power of the laser
50%。 In 1997, Mawst et al., University of Wisconsin, USA [52]
Laser-assisted chemical vapor deposition in InGaAs dual quantum wells
A ZnSe passivation layer is formed at the surface of the semiconductor laser cavity, which will connect the device
The COD threshold has been increased by 50%. Ressel, Germany, 2005
et al. [53] reported the cavity surface passivation of aluminum-free active region of high-power semiconductor excitation
Optical device, which exhibits excellent performance during the aging process of the laser.
In 2016, Beijing University of Technology used ion milling nitrogen passivation treatment
The cavity surface of the 980nm semiconductor laser is obtained, and the CW output power is obtained
at 22.5W, the output power of the device is increased by 32.14% [54].
In 2019, the Institute of Semiconductors of the Chinese Academy of Sciences adopted RF plasma
Body-enhanced reactive magnetron sputtering deposition of α-SiNx thin films to 980 nm
Photonic crystal lasers perform cavity surface passivation. By optimizing nitrogen-argon mixing
Plasma and rapid annealing are used to significantly inhibit it
COMD, which improves the performance of the device and the stability of the laser system
Sex [55]. In 2019, the Institute of Semiconductors of the Chinese Academy of Sciences was directly in a vacuum
Evaporation of a layer of ZnSe material with a thickness of 25nm as a passivation film,
It is used as a semiconductor by taking advantage of the large bandgap width of ZnSe thin film material
The passivation film on the surface of the laser cavity effectively improves the output work of the semiconductor laser
rate and device damage thresholds to provide cavity surface protection [56].

2.1.3.3 Coating technology
Cavity surface coating technology is a key process technology for high-power lasers
One of its functions is twofold: 1) covering the cleavage cavity surface to prevent active zones
oxidation, improve reliability and stability; 2) change the reflectivity of the cavity mask,
It enables the laser to achieve single-sided light output on the basis of maintaining performance
High laser output power and laser utilization efficiency. Because the cavity surface of the laser is the natural cleavage plane of the crystal (110 faces), its reflectivity
Approximately 31% when the laser is operating, due to the front and rear cavity surfaces of the laser
The magnitude of the reflectivity is the same, so that the two cavity surfaces emit light at the same time. open
Through the cavity surface coating, the anti-reflection coating and anti-reflection coating are prepared on the front and rear cavity surfaces of the laser
The highly reflective coating and the high-reflection coating reduce the threshold current, while the anti-reflection coating increases
Quantum efficiency and electro-optical conversion efficiency of the device.
There are two main contents of this technology: one is the film material
Choose. First of all, it is necessary to consider the high purity of the coating material, long-term stability,
Adhesion, thermal matching between the coating material and the natural cleavage plane
Force matching, lattice matching between coating materials, etc. At the same time, it should be easy
For evaporation, it will not damage the natural cleavage surface of the laser
Prevents the ambient atmosphere from diffusing into the luminous region of the device. The second is to determine the high anti-reaction
The reflectivity of the film and the transmittance of the anti-reflection coating are based on the following principles: after passing
The cavity surface emits as little light as possible, so that the laser light is transmitted as much as possible from the front cavity surface
At the same time, it does not cause obvious additional absorption and additional loss of cavity surface.
For anti-reflection coatings, the film material can be selected with a refractive index between the waveguide layer
The material between the effective refractive index and the refractive index of air. Usually chosen Al2O3、SiO2
As a low refractive index material, ZrO2、TiO2etc
It is a high refractive index material. The reflectivity of the high reflective coating is generally 95%
~98%, the reflectivity of the anti-reflection coating is generally 1%~5%.

2.2 High-power semiconductor laser beam combining technology
Side-emitting junction in the near-infrared band (750~1100nm).
Structural semiconductor lasers are the most mature and are currently used for pumping and The main form of high-power semiconductor laser source for processing. According to the laser sheet
The number of elements, the laser chip can be divided into a single tube and a linear array, the former is a single excitation
Optical unit, which can continuously output a few watts to tens of watts of power, the latter being several
The integration of the laser unit in the horizontal direction can continuously output tens of watts to
Hundreds of watts of power. For laser arrays, it is wide according to the direction of the integrated unit
degrees, which can be divided into a width of 10mm centimeter line array and a width less than
10mm mini line array. Place the laser chip horizontally or vertically
Toward a one- or two-dimensional overlay of light or a physical location overlay, and one further
step to increase the output power, as in the laser line array in the microchannel package
Vertically superimposed into a stacked array, which can output thousands of kilowatts of power, but also
This leads to a deterioration in its overall beam quality. How to get it when you increase the power
High beam quality diode lasers are key. Laser beam combining is solid
Now it is an effective technical approach for high-power, high-beam quality semiconductor lasers
one, which combines multiple units of light by geometric or physico-optical means
Synthesize a laser beam. According to the coherence of the combined beam laser unit, it is divided into:
Coherent and incoherent bundles. Coherent bundles require precise control of the closure
The spectral and phase characteristics of the beam unit are complex and coherent
The performance advantages of the beam diode laser source are not obvious and are not currently practical
Change. Incoherent bundles do not need to consider the coherence between the elements, technology
It is relatively simple, and it is the current practical high-power semiconductor laser beam light
The main implementation of the source. Incoherent beams can be divided into traditional beam combining techniques, dense wavelength beams, and spectral beams. The following is a pair of incoherent bundles
An overview of technological advances.

2.2.1 TBC technology
Conventional beam combining technology is based on standard diode laser chips, in:
During the beam closing process, the resonance in the cavity of the laser unit is not affected, and only through the outside
The optical element shapes the output beam of the laser chip, closes the beam spatially,
Polarization and wavelength combining to increase overall power and improve overall light
Beam quality is the main source for the realization of high-power diode lasers
Manner.
Among them, spatial beam combination is the use of refraction or reflection to divide multiple beams of light in
Spatial one- or two-dimensional stacking to increase power while beaming
deterioration of quality; Polarization beam combination uses the linear polarization characteristics of semiconductor lasers,
Two rays of linearly polarized light perpendicular to each other in the direction of vibration pass through the polarized beam
elements, in which P-polarized light is transmitted, S-polarized light is reflected, and the light field is realized
The near-field and far-field overlap, and the power is nearly doubled while the beam quality is increased
No change; Wavelength beam combining is to use the wavelength characteristics of laser light to combine beams through wavelength
element, where the wavelength λ1
The light is transmitted (reflected) at a wavelength λ2
Light reflection
(through), the two beams of light achieve the overlap of the near field and the far field, and the power is increased at the same time
The quality of the time beam does not change, and by using different wavelength beam elements, it can be
to achieve multiple beams of different wavelengths (λ1
,λ2,…,λn) of the laser beam, Kao
Considering the spectral width of the semiconductor laser itself, the spectrum is affected by temperature and current
Ring, etc., the interval between adjacent wavelengths of conventional wavelength bundles is generally not low
at 25 nm.

According to different package forms, based on conventional beam closing technology, it is currently available
Laser single-tube beam combination light source, linear array beam combination light source and stacked array beam combination have been developed
light source, which realizes direct output or fiber coupling in the range of tens of watts to tens of thousands of watts
Combined output, used in fiber laser pumping, laser processing, etc.
The single-tube beam-combining light source directly adopts the laser single-tube for beam combining
The heat source is relatively dispersed, the heat flux density is relatively low, and the same heat power is affected
Higher current drives can be used, and the laser unit can output more than ten
wattage and brightness of 1MW/(cm2·sr) after the beam is combined
It can output tens of watts to kilowatts from fiber with a core diameter of 100~200μm
The single-wavelength laser with a beam quality of 6~20mm·mrad has
High brightness, low cost and good reliability are used in fiber lasers
Pumps, laser medical, laser lighting and other fields. Especially in fiber optic excitation
Driven by the demand for optical pumping, the performance of single-tube combined beam light source has emerged
Rapid increase, while the cost has also dropped significantly. Reported by nLight in the United States
Using multiple high-power, high-beam quality 975nm laser single tubes,
The core diameter is realized by coupling the fibers after the spatial and polarization bundles are combined
The 105μm fiber has a continuous output power of 363W and a core diameter of 220μm
The continuous output power of the fiber is 1000W, which can be used for fiber lasers
of pumps [57]. Beijing Kaplin Optoelectronics Technology Co., Ltd. adopts 156
wavelengths are locked to 975.5 nm by a volume Bragg grating (VBG).
The laser single tube, through spatial superposition and polarization beam combination, makes the fiber with a core diameter of 200μm and a numerical aperture of 0.22 achieve an output of 1037W
Stabilized wavelength, narrow linewidth lasers [58] to increase fiber laser pumping
Efficiency.

The linear array beam light source mostly uses mini with relatively good beam quality
linear array (5~10 laser units) or centimeters with a low fill factor
linear array (fill factor<20%), single linear array power is 40~80W,
After bunching, the power is generally in the range of a few hundred watts to several thousand watts, coupled with the core diameter of the fiber
200~600μm, beam quality 20~60mm·mrad,
It is mainly used in industrial processing fields such as laser welding. Due to the single-tube closure
Rapid improvement in beam light performance through multiple single-tube combined beam sources
combination, has been able to achieve the performance indicators of the linear array beam light source, considering
to factors such as the cost and reliability of a single-tube beam source, linear array beam combination
There is a tendency for light sources to be replaced by single-tube beam light sources.
The stacked beam light source uses a laser line array in a microchannel package
beam, with the help of the efficient heat dissipation capability of the microchannel heat sink as well as the laser chip
Most of them are high-fill factor structures, and the output power of single-layer microchannel linear array is acceptable
Up to hundreds of watts, multi-layer line arrays can output thousands of watts to 10,000 watts after vertical superposition
Watt-level power, which can be boosted to higher water levels by combining wavelengths into beams
Flat. Laserline has developed a series of high-power optical fiber coupling products
Continuous output power from 1.5kW (core diameter 400μm, numerical bore
0.1 diameter) to 45kW (core diameter 2000 μm, numerical aperture size
0.2)[59]。 At present, the stacked array beam light source is mostly used for laser cladding and table
Surface hardening and other processes that require high laser power and low beam quality
In terms of industrial processing.

2.2.2 DWDM technology
The interval between adjacent wavelengths is not less than 25 nm relative to conventional beam combination
, dense wavelength combining can reduce the wavelength spacing to the nanometer level,
Without changing the beam quality, increase the number of laser units several times,
The power and brightness of the combined light source can be increased.
Key components of dense wavelength beam combination: 1) The center wavelength is stable and narrow
The linewidth laser unit can be etched directly on the chip or by the grating
It is realized by VBG external cavity feedback modulation spectroscopy; 2) The wavelength interval is relatively high
Small bundle elements, such as dichroic elements with high wavelength steepness, bundle combinations
VBG, etc.
Adopted by the Fraunhofer Institute for Laser Technology (ILT) in Germany
The grating method integrates a mini line array of 5 laser units directly in the grating method
Upper etching of different periodic gratings, 5 laser units output center wavelengths
5 lasers of different wavelengths spaced 2.5 nm apart [60], followed by 4
dichroic mirrors are bundled together and finally coupled into a 35 μm fiber [61]. should
The method of achieving a narrow linewidth cell structure is stable, but the chip grating worker
The requirements are very high, once the spectrum and position of a certain unit are related
If the deviation is present, the beam closing efficiency will be reduced sharply.

VBG cavity feedback is currently used to achieve narrow linewidth laser output
In the main method, the front cavity surface of the diode laser chip is coated with an anti-reflection coating, and the rear cavity surface and VBG form a resonant cavity, which is diffracted by VBG
The light is used as the seed light to control the oscillation spectrum, and the spectral width can be narrowed to 0.1 nm, temperature drift 0.01
Laser output at nm/°C. Based on
The technology, the German company DILAS from the core diameter 100
μm, numerical aperture
The output power is up to 410 in a fiber of 0.2
W[62]。 German ILT Research Institute
Research from the core diameter 100
Output in μm with a numerical aperture of 0.17 fiber
More than 800 power
W[63]; The institute also uses VBG as a bundle
element, through precision temperature control and angle adjustment 4 pieces VBG, to achieve 5
centers wavelength spacing 1.5
nm laser beam combining [64]. Germany
DirectPhotonics
Industries has also launched a power for 500~2000
W, the beam quality is 5
mm•mrad, core diameter is 100
μm fiber-coupled diode laser source products [65], which are used in:
Metal cutting field. The dense spectral beam combining technique will have a core diameter of 100
The output power of the μm fiber-coupled diode laser source is increased to
In the kilowatt range, the power and brightness are increased compared to conventional beam combiners
Nearly 1 order of magnitude.

2.2.3 SBC technology
Compared with the previous two, multiple beam elements are used to achieve multiple wavelengths
In the case of laser beam binding, spectral beam combining technology uses only a single dispersive element
Multi-beam wavelength spacing as low as 0.1 can be achieved
nm laser beam binding,
The number of beam merging units is further increased, and with the same beam quality,
Beam closing power and brightness have been increased.
The basic architecture of the spectral beam structure currently used is by Massachusetts, USA
Polytechnics were the first to report in 2000 that they did a lot to advance the development of this technology [66-68]. The basic structure of the bundle consists of the front cavity surface
Anti-reflection diode laser chips, conversion lenses, gratings, and external cavity mirror structures
The unit beam output by the laser chip is applied to the light through a transform lens
The gate is in the same position, and then the joint action of the grating and the external cavity mirror, partially
The light returns along the original path to form seed light, which assists the resonance in the cavity, and the light is partially straight
Output. The starting wavelength of the returned seed light strictly satisfies the grating square
, due to the different grating incidence angles of each sub-beam and the same diffraction angle,
The laser unit vibrates at different wavelengths and is transmitted through the external cavity mirror
The resulting laser light coincides in both the near and far fields, thus achieving beam power
is the sum of all the elements, the combined beam quality is the same as that of a single laser unit
to the laser output. After the transformation of technology, the United States Teradiode public
Division launched a power of 1 kW (Core diameter is 50.) μm)、2~12 kW
(Core diameter is 100.) μm) fiber output series products [69] and reported
The power is 360
W, 2x diffraction limit [70], brightness reached 10
GW/(cm2·sr) diode laser source, directly will be high power
The brightness of the semiconductor laser is increased by 2 orders of magnitude, which is high power and high brightness
The development of semiconductor lasers points to a new direction.

Table 1 is 12
At kW continuous output power, based on spectral beam binding
The brightness of semiconductor lasers compared to other commercial lasers can be
It can be seen that semiconductor lasers exceed CO2
Laser、Reached
The level of the Disk laser. At the same time, the spectral beam will also have a core diameter 100
The power of the μm fiber-coupled diode laser source is increased to 10,000 watts
Compared with conventional beam combining technology, its power and brightness have been increased by almost a lot
2 orders of magnitude.

The German Trumpf proposed a narrow-band filter for the outer cavity
The feedback wavelength locking structure [71] is applied through the coating to make the narrow-band filter
There is an angle-wavelength screening feature, and only the angle of incidence and wavelength are satisfied
The conditions under which the light can pass through the filter sheet, which makes the difference on the laser chip
The position of the laser unit vibrates at different wavelengths, and the wavelength adjustment is realized
System. Using this technology, further combined with grating technology, in 200 μm
The output power is more than 5 in the fiber with a core diameter kW[72]。
In addition to the above-mentioned near-infrared band, laser beam combining technology is applied to the above-mentioned near-infrared band.
It is also widely used in the visible and mid-infrared bands. subject to laser
Drives for displays, headlights, copper, gold and other metal processing applications,
GaN-based blue lasers have seen a blowout development in recent years. Nichia [73] in Japan, OSRAM in Germany [74], Japan
Panasonic [75] and other companies have successively launched high-power blue lasers
chips. According to Nichia, the strip width is 45
μm, cavity length 1.2 mm
The continuous power of the blue single-tube diode laser is more than 6 W, in 3
A current driven, 5.67
When the watt power is output, the electro-plug conversion effect
The rate reached more than 48 percent [76]. Laser line developed by OSRAM in Germany
The array output power reaches 107
W [77] and developed a -40 that can be satisfied ℃ ~+120
Blue lasers with an operating temperature of °C [78]. Blu-ray-based
Chip, using beam combining technology similar to the near-infrared band, Germany
Laserline [79], Coherent [80] and NUBURU [81]
and other companies have successively reported kilowatt-level blue lasers for copper welding, three-dimensional printing, etc. Among them, the core diameter of the United States NUBURU was reported 100
The μm fiber outputs a blue laser power of up to 1.5 kW。 Italy
Riva et al. [82] used wavelength spacing4
NM's 3 types of Blu-ray modules pass
Dense wavelength combined beam, from core diameter 50
Output power is achieved in μm fibers More than 100W。 Teradiode in the United States uses spectral beam combining technology
technology, achieved a power of 180
W, the beam quality is only1.26mm·mrad×1.31blue laser of mm·mrad[83],
The corresponding brightness reaches 1.1GW/(cm2·sr), which is also the current newspaper
The highest brightness of the blue laser.

3 Concluding remarks

In this paper, the common techniques of high-power semiconductor lasers are discussed
To summarize and introduce, it mainly includes edge high-power emitting semiconductor laser chips
and high-power semiconductor laser beam combining technology. High-power diode lasers
The range of applications covers almost all fields of optoelectronics. further
The development of high-power semiconductor laser technology is essential to promote China's optoelectronic collar
The development of domain disciplines, promote the development of China's laser industry, and promote the national economy
Upgrading and transformation is of great scientific, economic and strategic significance.

With the development of the demand for laser light sources in all walks of life, semiconductors
The demand for high power in lasers is never-ending. According to the application collar
The domain is different, and high power is no longer the only indicator. For industry
In terms of processing, in addition to further increasing the output power, it is also necessary to get it right
beam quality and brightness are further optimized; For different materials
When processing, it is also necessary to consider the absorption band, and use different wavelengths
The lasers are beam-combined, which requires a system of different substrate materials
high-power laser research and development; In order to further improve the beam closing power, also
It is necessary to further increase the spectral density of beam merging and study new beam combining technologies.
For pumping single-mode fiber amplifiers or by coupling single-mode fiber delivery
out of the application field, maintaining single-mode performance to facilitate single-mode fiber coupling
As the primary goal, on this basis, the output power is increased as much as possible; in the pump
Atomic clocks, pumped laser gyroscopes, pumped alkali metal lasers, separation
Laser isotopes, gas monitoring, fiber optic communications, satellite laser communications, etc
field, as much as possible while maintaining a single wavelength or narrow linewidth
Increase output power; For pumped fiber lasers, solid-state lasers, etc
For application scenarios with high absorption efficiency in a certain absorption band, it is required
To maximize the power of the useful band, so as to improve the pumping efficiency,
To reduce waste heat, it is necessary to increase the output power
Adjustment of the output spectrum and appropriate optimization.
Therefore, high-power semiconductor lasers will change according to the needs of the industry
Be refined and diversified. Customized for applications in different industries
The production of high-power semiconductor lasers will be the development of the futureDirection.