Type-II interband cascade lasers in the 4.3-4.7-/spl mu/m wavelength region

Operation of type-II interband cascade lasers in the 4.3-4.7-/spl mu/m wavelength region has been demonstrated at temperatures up to 240 K in pulsed mode. These lasers fabricated with 150-/spl mu/m-wide mesa stripes operated in continuous-wave (CW) mode up to a maximum temperature of 110 K, with an output power exceeding 30 mW/f and a threshold current density of about 41 A/cm/sup 2/ at 90 K. The maximum CW operation temperature of 110 K is largely limited by the high specific thermal resistance of the 150-/spl mu/m-wide broad area lasers. A 20-/spl mu/m-wide mesa stripe laser was able to operate in CW mode at higher temperatures up to 125 K as a result of the reduced specific thermal resistance of a smaller device.     

Improved CW operation of quantum cascade lasers with epitaxial-sideheat-sinking

First results on the epilayer-side mounting of quantum cascade (QC) lasers are presented. Operated in continuous-wave (CW) mode, these lasers are superior to substrate-bonded devices. The maximum CW temperature is raised by 20 K (up to 175 K), and, at comparable heat sink temperatures, the performance with respect to threshold current, output power, and slope efficiency is greatly improved for the epilayer-side mounted devices. QC-laser-specific mounting procedures are discussed in this letter, such as the high reflectivity coating of the back-facet and the front-facet cleaving after mounting. Modeling of the temperature distribution inside the QC laser shows a strong temperature gradient within the active waveguide core, which partly explains the still low maximum CW operating temperatures     

High-power continuous-wave quantum cascade lasers

High-power continuous-wave (CW) laser action is reported for a GaInAs-AlInAs quantum cascade structure operating in the mid-infrared (λ≃5 μm). Gain optimization and reduced heating effects have been achieved by employing a modulation-doped funnel injector with a three-well vertical-transition active region and by adopting InP as the waveguide cladding material to improve thermal dissipation and lateral conductance. A CW optical power as high as 0.7 W per facet has been obtained at 20 K with a slope efficiency of 582 mW/A, which corresponds to a value of the differential quantum efficiency η_d=4.78 much larger than unity, proving that each electron injected above threshold contributes to the optical field a number of photons equal to the number of periods in the structure. The lasers have been operated CW up to 110 K and more than 200 mW per facet have still been measured at liquid nitrogen temperature. The high overall performance of the lasers is also attested by the large “wall plug” efficiency, which, for the best device, has been computed to be more than 8.5% at 20 K. The spectral analysis has shown finally that the emission is single-mode for some devices up to more than 300 mW at low temperature     

Metal clad Pb1-xSnx Se/Pb1-x-yEuy SnxSe distributed feedback lasers

Distributed-feedback Pb_1-xSn_xSe double heterostructure stripe geometry diode lasers fabricated using molecular-beam epitaxy are discussed. These lasers operate in the CW mode up to 90 K and in the pulse mode up to 100 K. They are unique in their low tuning rate with injection current 4 cm^-1/A, and in that they withstand high CW injection currents without damage. These features are probably the result of the metal cladding layer located on top of the gratings     

Power, efficiency, and thermal characteristics of type-II interbandcascade lasers

High-performance mid-infrared type-II interband cascade lasers have been demonstrated under continuous-wave (CW) conditions with record-high wall-plug efficiencies (>14%) and output powers (>100 mW/facet) above 77 K. Device characteristics of these type-II interband cascade lasers are investigated systematically in terms of their output powers and efficiencies. Also, by comparing the temperature dependence of the threshold currents under pulsed and CW conditions, the thermal resistance and maximum heat sink temperature for CW operation are estimated for several mesa sizes. The limiting factors due to device heating for high-power/high-efficiency operation are identified and discussed in connection with device dimensions and packaging for the purpose of assessing further improvements     

Cryogenic operation of AlGaAs-GaAs vertical-cavity surface-emitting lasers at temperatures from 200 K to 6 K

We demonstrate for the first time the CW performance of AlGaAs-GaAs vertical-cavity surface-emitting lasers (VCSELs) at cryogenic temperatures from 6 K to 200 K. By detuning the cavity mode with respect to the gain peak so that optimum dc lasing operation is achieved at -100 K, we find that this optimum lasing performance can be maintained down to temperatures as low as 6 K. Across a broad range of temperatures from 200 K to 6 K, the minimum threshold current of a 16-/spl mu/m diameter VCSEL stayed below 4 mA, while its -3-dB modulation bandwidth increased by about 70% to 11 GHz at 6 K, and the external slope efficiency is greater than 70%.     

Mid-Infrared Raman Fiber Lasers

As mid-infrared (MIR) lasers show numerous applications in the field of defense, medical, materials processing, and optical communications. Investigation on MIR Raman fiber lasers (RFLs) increasingly becomes a hot topic. Compared with the traditional silica fibers, fluoride and chalcogenide glass fibers possess higher nonlinear coefficients and excellent MIR transmittances. In this article, the latest developments of the MIR RFLs using fluoride and chalcogenide glass fibers as gain media are introduced, respectively. This review article mainly focuses on the developments of MIR RFLs in aspects of output wavelength, output power, and optical efficiency. Besides, the prospect of MIR RFLs is also discussed.     

High performance CW 1.26 μm GaInNAsSb-SQW and 1.20 μmGaInAsSb-SQW ridge lasers

Long-wavelength GaInNAsSb SQW lasers and GaInAsSb SQW lasers that include small amounts of Sb have been successfully grown by gas-source molecular beam epitaxy (GSMBE) and processed into ridge lasers. The GaInNAsSb lasers oscillated under CW operation at 1.258 μm at room temperature. A low CW threshold current of 10.2 mA and high characteristic temperature (T₀) of 146 K were obtained for the GaInNAsSb lasers which is the best result for GaInNAs-based narrow-stripe lasers. Furthermore. The GaInAsSb lasers oscillated under CW operation at 1.20 μm at room temperature. A low CW threshold current of 6.3 mA and high characteristic temperature (T₀) of 756 K were obtained for the GaInAsSb lasers, which is also the best result for the 1.2 μm-range of highly strained GaInAs-based narrow-stripe lasers     

Cryogenic VCSELs with chirped multiple quantum wells for a very wide temperature range of CW operation

Cryogenic optical data links require an efficient optical source with temperature-insensitive continuous-wave (CW) operation at low temperatures. Also, to simplify optical alignment, it is desirable to obtain CW operation over a broad temperature range that spans both the low and high temperatures. By the use of vertical-cavity surface-emitting lasers (VCSELs) with chirped (nonuniform) multiple quantum wells (MQWs) to broaden the optical gain spectrum, CW operation has been achieved from 5-350 K, with improved characteristics in both the high- and low-temperature regimes. In particular, temperature-insensitive, submilliampere threshold current was achieved at temperatures from 5-50 K, with a threshold current density of 350 A/cm/sup 2/, and a threshold voltage that is below 3 V.     

High temperature operation of lambda =1.5 mu m tensile strained multiple quantum well SIPBH lasers

The high temperature operation of 1.5 mu m wavelength, strained-layer multiple quantum well, semi-insulating planar buried heterostructure lasers is reported. The lasers, which are grown by low-pressure organometallic vapour phase epitaxy and which have four 1.6% tensile strained In/sub 0.3/Ga/sub 0.7/As wells (thickness 8 nm), operate in CW mode up to heatsink temperatures of 140 degrees C. The CW output power at 100 degrees C is 26 mW per facet. These results are a marked improvement when compared to data reported thus far for 1.5 mu m wavelength lasers.<>     

Low-temperature optimized vertical-cavity lasers with submilliamp threshold currents over the 77-370 K temperature range

We demonstrate an extended temperature range (77-370 K) of continuous wave (CW) operation for dielectrically-apertured double-intracavity-contacted vertical-cavity InGaAs strained QW lasers optimized for operation at cryogenic temperatures. Superior performance is achieved through the alignment of the cavity mode with the gain of the first and second quantized subbands at 77 K and room temperature, respectively. This design results in submilliamp threshold currents over a 77-370 K temperature range for 5.4-/spl mu/m diameter lasers. The threshold is 120 /spl mu/A and the output power is >8 mW at 77 K.     

High-temperature operation of 1.55 ?m InGaAsP double-channel buried-heterostructure lasers grown by LPE

High-temperature operation of InGaAsP double-channel buried-heterostructure (DCBH) lasers emitting at 1.55 ?m is reported. The 1.55 ?m InGaAsP DCBH lasers have threshold currents as low as 18 mA at 20°C. The threshold current temperature sensitivity between 10°C and 75°C is characterised by a T0 value of 55?66 K. Electro-optical derivative measurements show that the 1.55 ?m InGaAsP DCBH laser does not have substantial above-threshold leakage current for junction temperatures as high as 75°C. Finally, these devices were operated at temperatures as high as 110°C, the highest CW operating temperature obtained to date for a 1.55 ?m InGaAsP laser.     

Pb1-xSnxTe/PbTe1-ySeylattice-matched buried heterostructure lasers with CW Single mode output

The first successful realization of buried heterostructure diode lasers in the PbSnTe/PbTeSe system is reported. This has resulted in routine cw operation above 80 K with threshold currents as low as 60 mA in 5 µm wide stripe lasers. CW operation has been achieved to 120K. In addition, these lasers operate in the fundamental transverse mode up to as much as four times threshold.     

Resonant-phonon terahertz quantum-cascade laser operating at 2.1 THz (/spl lambda//spl sime/141 /spl mu/m)

The development of quantum-cascade lasers (QCLs) at 2.1 THz (/spl lambda//spl sime/141 /spl mu/m), which is the longest wavelength QCL to date without the assistance of magnetic fields, is reported. This laser uses a structure based on resonant-phonon depopulation, and a metal-metal waveguide to obtain high modal confinement with low waveguide losses. Lasing was observed up to a heatsink temperature of 72 K in pulsed mode and 40 K in continuous-wave (CW) mode, and 1.2 mW of power was obtained in CW mode at 17 K.     

2.0-/spl mu/m single-mode operation of InGaAs-InGaAsP distributed-feedback buried-heterostructure quantum-well lasers

Distributed-feedback (DFB) buried-heterostructure (BH) lasers with quantum-well active region emitting at 2.0 /spl mu/m have been fabricated and characterized. The lasers with four wells showed performance of practical use: threshold current as low as 15 mA for 600-/spl mu/m-long devices and CW single-mode output up to 5 mW at 2.03 /spl mu/m under operation current of 100 mA were observed. The current- and temperature-tuning rates of DFB mode wavelength are 0.004 nm/mA and 0.125 nm/K, respectively.     

1.55 ?m InGaAsP low-threshold buried-crescent injection laser

Fabrication of 1.55 ?m InGaAsP buried-crescent (BC) injection lasers with a p-n-p-n blocking structure is described. The BC lasers exhibit a threshold current as low as 14 mA at 25°C, very high yield, output power more than 10 mW and high-temperature operation up to 80°C. These BC lasers have continued to operate in stable CW mode at 50°C for more than 1000 h. The lifetime of the 1.55 ?m InGaAsP lasers at 50°C is estimated to exceed about 2.5 × 104 h.     

Room-temperature continuous-wave operation of InAs quantum-wire laser on InP(001) substrate

A self-assembled quantum-wire laser structure was grown by solid-source molecular beam epitaxy in an InAlGaAs-InAlAs matrix on InP(001) substrate. Ridge-waveguide lasers were fabricated and demonstrated to operate at a heatsink temperature up to 330 K in continuous-wave (CW) mode. The emission wavelength of the lasers with 5 mm-long cavity was 1.713 /spl mu/m at room temperature in CW mode. The temperature stability of the devices was analysed and the characteristic temperature was found to be 47 K in the range of 220-320 K.     

Mid-infrared type-II interband cascade lasers

Interband cascade (IC) lasers that utilize optical transitions between the conduction and valence bands in a staircase of Sb-based type-II quantum wells (QWs) represent a new class of mid-IR diode lasers. By combining the advantages of quantum cascade lasers and type-II QW interband lasers, type-II IC lasers show promise of operating in continuous-wave (CW) mode up to room temperature with high output powers. Significant advances toward such high performance have been reported in terms of record-high differential external quantum efficiency (DEQE>600%), peak output power (~6 W/facet at 80 K), CW power conversion efficiency (>16% at 80 K), and room-temperature operation under pulsed conditions. Here, we will review the progress made in the past few years and discuss the issues encountered during the development. Also, the current status of type-II IC lasers and the remaining challenges will be discussed     

Operating characteristics of single-quantum-well AlGaAs/GaAshigh-power lasers

The operating characteristics of six types of graded-index separate confinement heterostructure single-quantum-well wide-stripe lasers grown by metalorganic chemical vapor deposition are reported. The lasers exhibited intrinsic mode losses as low as 3 cm^-1 and internal quantum efficiencies near unity. Measured differential gain coefficients range from 3.7 to 6.5 cm/A, and extrapolated transparency current densities range from 54 to 145 A/cm². These wide-stripe lasers are typically multilongitudinal mode and exhibit narrowing of the gain envelope and lateral far-field pattern as the cavity length increases. The high value of T₀(>200 K) at long cavity lengths in conjunction with the low current density permits junction-side-up operation to CW optical powers of 0.5-0.7 W/facet, at which level catastrophic facet damage occurs on the uncoated devices. A maximum power conversion efficiency of 57% was measured on the laser structure exhibiting the lowest threshold current     

基于GaInAs/AlInAs中红外量子级联激光器的自洽电子子带能级结构研究

中红外(Mid-infrared, MIR)量子级联激光器(Quantum Cascade Laser, QCL）已被广泛应用于定向红外对抗、自由空间光通信、痕量气体传感等重要领域。利用Nextnano++软件进一步完善了自洽计算基于MIR QCL器件的薛定谔方程和泊松方程的理论方法。针对InP衬底上生长的GaInAs/AlInAs多量子阱MIR QCL器件,研究了四能级双声子共振QCL结构中有源区的电子子带能级结构,并对这些子带能级随器件工作温度、驱动电场、注入区掺杂浓度等变化的规律进行了系统研究,获得了与实验结果一致的理论结果。此工作为MIR QCL器件的生长和制备提供了理论设计和研究方法,为了解器件工作条件提供了理论预期,也为进一步提高MIR QCL的发光功率和效率提供了理论研究支撑。