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The vertical external cavity surface emitting laser (VECSEL) is one of the hottest research fields of semiconductor lasers, due to its high power and good beam quality. However, there are few reports about how to systematically design the active region of VECSEL. In this paper, the gain design of quantum wells, which are the most important region within the VECSEL, is carried out. To achieve low power consumption under high temperature condition, epitaxial structure of the VECSEL is optimized by using the commercial software PICS3D. Firstly, the relationship between the structure of quantum well and the gain is simulated by the k·p method. Then, the gain spectra of quantum wells at different carrier densities and temperatures are compared with each other, and the optimal composition and thickness of quantum well are thus determined. The temperature drift coefficient is 0.36 nm/K, obtained by simulating the drift of the gain peak wavelength at the working temperature. Finally, the gain spectra of quantum wells with five different barriers are compared with each other. The slight blue shift of the gain peak in the quantum well with five different barriers accommodates the different emission thermal drifts of the quantum well at high temperature operation. With the GaAsP barriers on both sides of quantum well the gain characteristics of quantum wells can be improved efficiently. The designed structure is deposited by the MOCVD system. According to the reflection spectrum of the gain chip, measured by ellipsometer, the stop-band over 100 nm is centered at the about 970 nm wavelength, confirming accurate growth of the VECSEL. The 808 nm pump laser is focused on the surface of VECSEL chip at an incident angle from 30° to 50°. The VECSEL light-light characteristics are tested under the output coupling mirror with different reflectivity. The output power of VECSEL with a 97.7% reflectance output coupling mirror reaches 9.82 W at the pumping power of 35 W, without saturating the power curve. By using the external mirrors with different reflectivity, there appears the wavelength shift with the pumping power changing from 0.216 nm/W to 0.16 nm/W. Thus, the internal heating effects are different for VECSEL with different mirrors. The divergence angles at two orthogonal directions are 9.2° and 9.0°, respectively. And the circle profile of optical field shows good symmetry.

WC-17Co cermet coatings were deposited on Ni718 alloys using the high-velocity oxygen fuel (HVOF) technique. These coatings were then heat treated by different processes (150 °C, 10 h; 300 °C, 10 h; 450 °C, 10 h). The effects of heat treatment on microhardness, elasticity modulus, and fracture toughness were studied by an indentation method. The residual stresses of the coated specimens were evaluated by the Almen strip method. The results show that the phase constitution and the structure of the WC-17Co coatings exhibit no obvious change in 150, 300, and 450 °C heat-treatment. The microhardness, elasticity modulus, and fracture toughness of the WC-17Co coatings decrease with the increase of heat treatment temperature. The descent tendency of the mechanical properties is attributed to the decline in compressive residual stresses after isothermal heat treatment.

To shape the beam with two-lobe far-field property from a dual side Bragg reflection waveguide semiconductor laser, a dual grating structure based on surface plasmons was prepared on the optical outlet facet of a Bragg reflection waveguide. It could combine the two lobes into a single lobe and to increase the optical intensity and quality of the beam. An Au-SiO2 grating was used to couple photons into surface plasmons and to combine the two lobe beams into a single beam. The surface plasmons also were taken to increase the extraordinary optical transmission. On the other hand, the Au-Si3N4 grating was used to help the outlet surface plasmons couple back to photons, meanwhile collimating the outlet beam to increase the far-field property. Numerical simulation results indicate when the parameters for Au-SiO2 show a depth of 50 nm, a filling factor of 0.5 and a duration of 350 nm, and those for Au-Si3N4 show 70, 0.5 and 660 nm, respectively, the outlet far-field beam will has a 6.1 divergence, which means the divergence angle shrinks by 3.6 times as that without the dual grating structure. The far-field optical transmission power reaches 62% of the model source, that is 1.59 times of the power of a single lobe far-field to the structure without the dual grating. Moreover, the cavity facet reflectivity has reduced to 12.4%, 0.53 times as the structure without the dual grating. It concludes that the dual grating structure has optimized the far field properties of dual side Bragg reflection waveguide semiconductor lasers.

For the special requirements of the exciting source of a 87Rb based atomic clock for the miniaturization and high temperature conditions, a 795 nm Vertical Cavity Surface Emitting Laser(VCSEL)corresponding to the Rb atom energy level transition was designed and fabricated. Firstly, the energy levels and material gains of the InAlGaAs/AlGaAs Multiple Quantum Wells (MQWs) were calculated by the kp method to optimize the compositions and thicknesses of the quantum wells. Then, a Distributed Bragg Reflectors(DBRs) at 795 nm were designed and their reflection characteristics, longitudinal optical fields and averaged doping profiles were calculated and optimized using a one-dimensional transfer matrix method. Finally, the epitaxial structure of the 795 nm VCSEL with optimized MQWs and DBRs were grown on a GaAs substrate by Metal Organic Vapor Phase Epitaxy (MOVPE) and the oxide-confined 795 nm top-emitting VCSELs with unclosed-mesa structures were fabricated and characterized. Experimental results indicate that the packaged VCSELs can keep lasing under a cw current from 25 C to 85 C with power decreasing from 17 mW to 1.8 mW, the far field profiles are circular with a divergence angle of 15 and the temperature-shift of the lasing wavelength is 0.064 nm/C. Moreover, the lasing wavelength moves to the wavelength required by 87Rb atoms at an ambient temperature of 52 C and a current of 100 mA. The 795 nm VCSELs satisfy the basic requirements of 87Rb based miniaturized atom clocks for stable operation in a special wavelength and high-temperatures.

Semiconductor laser is one of the most critical components in the field of modern communication. Research and development of single-mode semiconductor laser with high stability, high power, high beam quality and narrow line width is an important research area in this field. In this paper, A novel edge-emitting semiconductor laser diode structure is proposed. In the structure an active multimode interference waveguide structure serves as a main gain region. To modulate the longitudinal mode of the laser, a gain-coupled distributed feedback(DFB) laser based on high order surface gain coupled grating is introduced into the structure as well. The novel structure is then fabricated and compared with an conventional DFB laser. The experimental results show that higher slope efficiency and output power are achieved with the proposed structure than those with the conventional distributed feedback semiconductor lasers. The novel structure is also compared with conventional MMI laser with only Fabry-Parot(FP) cavity. The result shows that the proposed structure has higher beam quality and better stability than the FP cavity multimode interference waveguide lasers. To enhance the gain contrast in the quantum wells without introducing the effective index-coupled effect, the groove length and depth are well designed. Our device provides a single longitudinal mode with the maximum CW output power up to 53.8 mW/facet at 981.21 nm and 400 mA without facet coating, 3 dB linewidth < 13.6 pm, and SMSR > 32 dB. Optical bistable characteristic is observed with a threshold current difference. Meanwhile, by using high-order distribution feedback grating formed by shallow surface etching in the process of chip design and fabrication, the proposed structure of laser diode can realize regrowth freely and only micron-scale precision i-line lithography is required. Such a structure with simple fabrication process and low manufacturing cost has great potential for commercial mass production.

We designed a new type of plasmonic laser source based on the Bragg reflection waveguide. This laser source is simple in structure and convenient for integration. It works under room temperature electrical pumping condition and outputs plasmonic laser with more than milliwatt power, which is much larger than those demonstrated plasmonic laser sources with power of nano-watt scale. The proposed laser works at 808 nm. The tilted light beam offered by Bragg reflection waveguide directly couples into surface plasmon polaritons in our quasi-Otto configuration.

Single emitter diode laser has better beam quality and longer lifetime as compared with a diode laser bar.However,its application to the material processing is limited by its lower output powers.To improve the output power of the single emitter diode laser,this paper proposed an optical fiber coupling method for single emitter diode lasers based on the polarization multiplexing.Firstly,16 single emitters were divided into two laser groups,and the laser beam from the two groups was combined into one by spacial multiplexing technology.Then the beam was combined by polarization multiplexing again.Finally,a focusing system developed by ourselves was used to couple the combined beam into an optical fiber to improve the output power of the optical fiber coupling module.Experimental results show that the laser output of the module can reach 67 W from a fiber with a fiber core of 200 μm and a Numerical Aperture(NA) of 0.2 when the working current is 5.8 A.Moreover,the coupling efficiency of the module has reached 84%.This high power LD module can meet the requirements of plastic processing in power and beam quality.

A high brightness 808 nm edge-emitting diode laser based on the dual-sided Bragg reflection waveguide was reported.The 10 μm-wide ridge lasers with uncoated facets demonstrated more than 650 mW power in quasi-continuous-wave operation,being limited by the thermal rollover of the unmounted devices.A nearly circular output beam is obtained due to the significantly expanded modal spot size.The beam divergence with full-width at half maximum was as narrow as 8.3° and 8.1° respectively in the vertical and lateral directions.

A kind of metal gratings based on surface plasmon coupling was presented in this paper.The metal grating has different transmission rate according to incident direction because of different surface plasmon coupling conditions.The unsymmetrical transmission phenomenon appears for the Au-SiO2 grating when the periodic is 500 nm and the filling factor is 0.7,particularly for wavelength from 565 to 589 nm.A maximum transmission contrast of more than 3 × 104 is found at filling factor 0.662.When the thickness of Au is 60 nm,the transmission contrast is more than 5 during 570 ～ 630 nm,and the maximum transmission is 43%.When the periodic is 1 100 nm,the transmission contrast is more than 5 during 1 530 ～ 1 590 nm,which satisfies for the mid-infrared applications.

The laser processing is widely used in the welding of metallic materials,cladding,surface hardening,and other industrial fields.The semiconductor laser has many advantages,such as small volume and weight,high efficiency,maintenance-free,low cost,short wavelength,and so on.In this paper,a 2 218 W high-brightness fiber-coupled module was designed and overall assembled by using 48 conduction cooled diode laser arrays as light-emitting units under a major thoroughfare of industrial water-cooling condition.The emitting wavelength of the diode laser arrays were 808,880,938,976 nm,respectively.The high brightness module can make the flexible manufacturing directly applied in the industrial.

Both tapered structure and broad-stripe semiconductor laser diodes were fabricated based on the AlGaAs/AlGaAs epitaxial layers with a graded-index waveguide separated confinement hetero-structure under the excited wavelength of 850 nm.The temperature characteristics of the devices were investigated and compared at the temperatures between 20 ℃ and 70 ℃.Experiments show that the measured characteristic temperature(164 K) of the tapered devices is much higher than that of the broad devices(96 K) and the wavelength-shift coefficients of the tapered and broad-stripe devices are 0.25 nm/K and 0.28 nm/K respectively under a duty cycle of 0.5%(t=50 μs,f=100 Hz) and a pulsed current of 1 000 mA.When the temperature is below 50 ℃,the Full Width at Half Maximums(FWHMs) of the tapered devices and the broad-stripe devices are 1.12 and 1.24 nm,respectively.These results indicate that the tapered lasers have better temperature characteristics than the broad ones with the same epitaxial structure under certain temperature conditions.

As civil diode laser cladding sources rely heavily on import from the occident,this paper developed a diode laser source which could continuous output ten thousands of watt powers.The light paths of the diode laser was simulated by ZEMAX,including the designs of beam arrangement,collimation lens and focus units.Four diode laser stacks with wavelengths of 915 nm and 976 nm respectively were used in an experiment and their beams were combined by the technologies of polarization combination and wavelength combination.A focusing experiment was performed by the focusing system developed by oursevles and the experiment results show that when an current of 122 A is inputted,the output power and the total electrical-optical conversion efficiency of this laser cladding source are 10 120 W and 46%,respectively,and the beam spot size is 2.5 mm×18 mm at working surface.This diode laser source can meet the need of large area and rapid laser cladding and heat treatment in industry.

The continuous-wave single-mode operation of edge-emitting diode laser based on dual-sided non-quarter-wave Bragg reflection waveguide (BRW) was demonstrated at room temperature. A low-index core was utilized in the laser. The ridge BRW lasers (BRLs) exhibited an ultra-narrow twin-beam output. Single longitudinal mode emission with a very small spectral linewidth of 0.052 nm was measured. The lasing spectra showed a periodic modulation in the envelope with a mode spacing of approximately 3.3 nm. When the injection current of the BRLs was beyond 300 mA, a large mode hopping of the emission wavelength was observed.

By taking twelve 976 nm diode laser short bars as emitting units,a high power fiber coupled diode laser module with several hundred watts was developed.Firstly,the laser beam emitting from each diode laser short bar was shaped by a Beam Transform System(BTS) and a cylindrical lens,by which fast and slow axis beam parameter products could be symmetrized and the divergence was similar in the two directions.Then,every six diode laser short bars made up a laser stack by spatial multiplexing technology in the perpendicular direction and the laser beams from the two laser stacks were combined by polarization multiplexing.Finally,optimized triplet lens focused laser beams into a single multimode fiber.Experimental results indicate that the continues wave optical power of the coupled diode laser module can reach to 418 W from the multimode fiber with a core diameter of 400 μm and numerical aperture of 0.22,and its brightness is 2.19 MW/(cm2·sr).Matlab software was also applied to research of the near field intensity distribution of the laser spot output from the fiber and the result shows that the intensity distribution is a top hat,which proves that the module can be used in numerous applications like the welding and hardening of metal.The optical spectrum was also measured to determine the heat dissipation of the device and the result shows that the center wavelength of the device has shifted 6.8 nm with the driving current increasing from 20 A to 50 A,and the spectral width is just 4.12 nm(Full Width at Half Maximum,FWHM) for the diode laser short bar at the current of 50 A,which indicates that the device is favorable to the heat dissipation and could reliably work for long time.As compared with other candidates,the designed module has higher conversion efficiency and fiber output powers,and is suitable for the fields of material process and laser pumping.

A nano-Zno films are deposited on the Mo film/ceramic substrates by using the electron beam vapor deposition technique. Then a hydrogen plasma treated method is used to improve the characteristics of ZnO thin films by microwave plasma chemical vapor deposition system. Effects of process parameters on morphologies and structures of the ZnO thin films are detected and analysed by field emission scanning electron microscopy, X-ray diffraction spectrum and energy dispersive spectrum. The experimental result indicates that the hydrogen plasma treated techniques can essentially reduce the surface resistance and improve the field emission current density of the nano-ZnO thin films. For the hydrogen plasma treated sample, its field emission current density can increased more than three times at 2.2 V/microm electric field condition.

An optical system to perform the semiconductor laser myringotomy with the help of a video display and a pilot laser was designed and manufactured.First,the 650 nm laser output from a single emitter and the 810 nm laser emitted from a laser diode array were coupled into a fiber with a core diameter of 200 μm and a numerical aperture of 0.22 by using beam shaping and wavelength beam combination technologies.Then,an achromatic lens was used to collimate the dual wavelength laser output from the optical fiber and the other achromatic lens which could move along principal axis and consequently change the spot size was used to focus the dual wavelength laser to the eardrum.Meanwhile,laser and imaging lights were coupled as coaxial by using a hot mirror and the imaging components from markets.Moreover,the location of myringotomy could be piloted by red light on a computer monitor.According to the results of measurement,the laser power output from the system can be continuously adjusted from 0 to 13.3 W,and the spot size can also be adjusted between 1-3 mm.The system can decrease the operation time and the possibility of surgery side effect;moreover,the myringotomy for children needs not any anasthesia.In addition,the system has the virtues of low volume,light weighted and high wall-plug efficiencies compared with other candidates.

Three 976 nm diode laser short bars were used as submodule to manufacture high brightness fiber coupled module with CW hundred watts class output power.First,beam transform systems were employed to shape beams emitted from each submodlue;Second,the three beams were stacked in direction of lower beam parameter product by means of spatial multiplexing technology;Finally,the laser was focused into a multimode fiber with 200 μm core diameter and NA=0.22 by optimized lens.Experiment result showed that divergence angle of the focused laser beam was 24.8° and its beam waist diameter was 175.2 μm;laser output from fiber could reach to 107 W,equalizing brightness of 2.23 MW/(cm2·sr),which is a higher level in China.Furthermore,the wall plug efficiency is 43.1% when driving current is 52.5 A,which is far higher than that of solid state laser.Finally the thermal resistance was computed by means of measuring spectrum with different current and the result is 1.29 K/W which indicates favorable heat dissipation of the module.All of the result showed that the module can be used in the field of pumping fiber lasers,medical,material processing and so on.

The effect of the output power on difference passivation facet in 980 nm graded index waveguide structure InGaAs/AlGaAs laser diodes was studied.The output power of the 980 nm laser diodes with no facet passivation,Si passivation,and ZnSe passivation at the front and the back facet were compared.The test results show that output power of the ZnSe passivation method is 11% higher than Si passivation method,and is 42% higher than no facet passivation.The laser diode of no facet passivation is failure at the current is 4.1 A,the Si passivation is 5.1 A,ZnSe passivation is 5.6 A.The reasons of failure for difference passivation were analyzed.In conclusion,the method of ZnSe passivation facet can increase the output power of semiconductor lasers.

The design principles and design methods are introduced for a InP-based Quantum Cascade Laser(QCL) with high power and short wavelength.According to the described ideal and real carrier transition paths,the active region designing trends and approaches to enhance the efficiency of the QCL are also proposed.The most advanced design methods,such as two phonon resonance design,nonresonant extraction design,strong coupling design,deep well design,shallow well design and short injector design are reviewed,respectively.The characteristics and advantages of each design method are discussed.With these highly advanced design approaches,the Wall-plug Efficiency(WPE) of the short wavelength QCL exceeds 50% at low temperature and room temperature,continuous wave operation surpasses 3 W and the maximum T0 and T1 reach 383 K and 645 K,respectively.As the most advanced working region,high power,advanced design methods make QCL unlimited usage in both military and civilian fields.Moreover,they could also be served as the highly efficient bandstructure pioneer design methods for other working regions.

Two 915 nm diode laser short bars were used as sub-module to manufacture high brightness fiber coupled module with continuous wave(CW) output power.Firstly,beam shaping technology was employed for each sub-module to enhance its beam quality.Secondly,the two beams were stacked in direction of lower beam parameter product by means of spatial multiplexing technology.Finally,the laser was focusing into a multimode fiber with 200 μm core diameter and NA=0.22 by optimized lens by focusing lens.Experiment results show that the beam waist diameter at focal plane is 105.4 μm when driving current is 52.5 A,the optical power output from fiber can reach to 72.6 W with a brightness of 6.08 MW/(cm2·sr),and the wallplug efficiency is 42.2% when driving current is 52.5 A.The character of heat dissipation was studied by means of measuring spectrum with different current,and the results prove that the module has favorable heat dissipation.

To improve the output powers of Vertical Cavity Surface Emitting Lasers(VCSELs),a 977 nm VCSEL array with three In0.2Ga0.8As/GaAs0.92P0.08 strained Quantum Wells(QWs) was studied.The structures of the QWs were optimized and GaAsP with a larger band gap was chosen as the barrier material,and the band offsets of In0.2Ga0.8As/GaAs0.92P0.08 were calculated.The output powers of the devices which used In0.2Ga0.8As/GaAs0.92P0.08 and In0.2Ga0.8As/GaAs QWs were simulated theoretically and analyzed comparetively,respectively and the pulsed peak powers of two array devices were measured.Then,the performance of the array device was estimated by a functional method using a p-parameter determined by the turn-on voltage,threshold current,and the differential resistance.Experimental results show that the 4×4 VCSEL array with In0.2Ga0.8As/GaAs0.92P0.08 QWs and an emitting area of 0.005 cm2 can achieve a pulsed peak power of 123 W when the injecting current is 110 A,and its power density and slope efficiency are 45.42 kW/cm2 and 1.11 W/A,respectively.This output power is 13 % larger than that of the array with In0.2Ga0.8As/GaAs QWs and the same emitting area.Furthermore,the values of p parameter are 15 and 13 under CW operation and pulsed operation,respectively,which indicates that the device has relatively good performance.In conclusion,the 4×4 VCSEL array with three In0.2Ga0.8As/GaAs0.92P0.08 strained QWs is able to achieve higher output powers.

A hundred-watt level semiconductor laser air cooling system was analyzed by ANSYS finite element analysis software.The temperature distribution and air cooling system of this high-power semiconductor laser module were simulated and optimized.It provides the basis of the choice program for 100 W-class high-power semiconductor laser module air cooling technology,and the relative experiment has been verified.

The growth rate and surface structure of AlGaAs sample were investigated by employing the optical in-situ monitoring technique.In situ monitoring of optical time resolved normalized reflectance(NR) and reflectance anisotropy(RA) in growth process of multilayer AlxGa1-xAs sample was carried out.Oscillation characteristics of NR curve was analyzed.Converged value of NR and RA curve changed monotonously with Al composition at the monitoring optical energy of 1.9 eV.The growth rate was gained from fitting the NR transient.And the deviation of calculated growth rate was lower than 0.02 nm/s compared to the SEM measurement results.From the analysis of time resolved RA curve,surface reconstruction caused by the growth temperature was observed during the epi-growth of GaAs layers.

To improve the wire bonding and homogeneous injecting currents,this paper proposes a Vertical Cavity Surface-emitting Laser(VCSEL) array with a non-closed structure.In this structure,a non-closed groove is etched to form a mesa for simplifying the processing and reducing the damage of devices.The 850 nm VCSEL arrays(including 2×2,3×3 and 4×4 array devices) with the non-closed type top emission structures are tested and analyzed.Results show that the continuous output powers are up to 80,140 and 480 mW at room temperature,threshold currents are 0.15,0.25 and 0.4 A,and the far-field divergence angles in parallel and vertical directions are 9° and 9.6°,13.5°and 14.4°,15° and 14.4°,respectively.In the context of a pulse width of 50 μs and a pulse repetition rate of 100 Hz,the maximum output powers are 90,318 and 1 279 mW and the threshold currents are 0.2,0.5 and 0.7 A,respectively.The power curves of chips are tested before and after packaged.The result shows that the heat saturation current of the chip after packaged is much higher than that of the chip before packaged,which suggests that good packaging can improve the cooling efficiency and reduce the effect of internal heating on the device performance.

As 808 nm single emitter diode lasers have low output powers,they are limited to pump neodymium-doped double-cladding fiber lasers in end pumping.In order to enhance the pumping efficiency of the fiber laser by using single emitters,a fiber coupled module with several single emitter diode lasers was developed.First,the fast axis and slow axis of each diode laser were collimated by a micro-lens.Then,the output beams of diode lasers were combined with reflecting prisms.Finally,a suit of optical system designed by ourselves was utilized to expand and focus the beam into a optical fiber.Experiments show that this approach can greatly increase the brightness of the module with fiber coupled LDs.Four LDs with continuou output power of 5 W are coupled in a 105 μm multimode optical fiber with a core diameter of 105 μm and a numerical aperture of 0.2 when the working current is 5.8 A,it can offer the fiber output power of 15.22 W,coupling efficiency of 74% and the brightness over 1.4 MW/cm2·sr.

Conventional semiconductor lasers suffer from the scale of the diffraction limit due to the light to be confined by the optical feedback systems.Therefore,the scales of the lasers cannot be miniaturized because their cavities cannot be less than the half of the lasing wavelength.However,lasers based on the Surface Plasmon Polaritons(SPPs) can operate at a deep sub-wavelength,even nanometer scale.Moreover,the development of modern nanofabrication techniques provides the fabrication conditions for micro-or even nanometer scale lasers.This paper reviews the progress in nano-lasers based on SPPs that have been demonstrated recently.It describes the basic principles of the SPPs and gives structures and characteristics for several kinds of nanometer scale lasers.Then,it points out that the major defects of the nanometer scale lasers currently are focused on higher polariton losses and the difficulties in fabrication and electronic pumping technologies mentioned above.Finally,the paper considers the research and application prospects of the nanometer scale lasers based on the SPPs.

Dry etching of InP material based on inductivity coupled plasma(ICP) was thoroughly studied,Cl2/Ar/H2 gas mixture was adopted,and the etching depth could reach 10 μm with a vertical and a smooth surface.The gas percentages of the total gas versus etching rate,and the applicable regions of Ni,SiO2,and the combination of Ni and SiO2 were studied,respectively.The regions of the effective etching rate and selectivity against Ni are 450~1 200 nm/min and 175~190,respectively.The choosing and fabrication approaches adopted are highly suitable for any semiconductor material based on ICP system.