Heterostructure Laser Diodes Research Articles

High-Reliable and High-Speed 1.3 $\mu$m Complex-Coupled Distributed Feedback Buried-Heterostructure Laser Diodes With Fe-Doped InGaAsP/InP Hybrid Grating Layers Grown by MOCVD

In this paper, we report the fabrication of high-reliability and high-speed 1.3 mum complex-coupled distributed feedback (CC-DFB) buried heterostructure (BH) laser diodes (LDs) with Fe-doped InGaAsP/InP hybrid grating layers. High optical coupling coefficient and eminent current confining ability are accomplished by combining the Fe-doped InGaAsP/InP current-blocking-grating (CBG) layers to provide both the distributed-feedback index-and gain-coupling coefficients. Besides, the narrow-stripe BH LDs are implemented by burying the active region with a Fe-doped InP current-blocking layer during the epitaxial regrowth. The fabricated CBG CC-DFB BH LDs at 20degC shows a low threshold current of 5.3 mA, a maximum light output power of 36 mW at 100 mA, a high slope efficiency of 0.41 mW/mA, and a side-mode suppression ratio (SMSR) of 42 dB at twice the threshold. In addition, these LDs exhibit a maximum operation temperature of 125degC, an extremely low threshold current of 15.8 mA at 90degC, a small variation in slope efficient of only -1 dB in the temperature range from 20degC to 80degC, and a characteristic temperature of 77 K and 56 K between 20 degC and 60degC, and 70degC and 120degC, respectively. Furthermore, these 1.3 mum CBG CC-DFB BH LDs exhibit a high-speed characteristic up to 11.8 GHz at room temperature and an estimated median lifetime of more than 1.1 times 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> h or 12.5 years at 5 mW and 85degC.

Reduced free carrier absorption loss in midinfrared double heterostructure diode lasers grown by liquid phase epitaxy

An improved InAsSb∕InAsSbP double heterojunction ridge laser was designed and grown by liquid phase epitaxy. The cladding layer absorption loss was minimized by the introduction of two undoped quaternary layers on either side of the active region to form a five layer epitaxial structure. The inserted layers also helped alleviate interdiffusion of unwanted dopants into the active region and reduced current leakage in the device. The resulting diode lasers operate readily in pulsed mode near 3.5μm at elevated temperatures and with a threshold current density as low as 118Acm−2 at 85K. Compared to the conventional three-layer double heterostructure laser, the modified structure with reduced optical loss increased the maximum lasing temperature by 95–210K.

Diode laser spectroscopy of CO 2 at 790 nm

Absorption lines of 12C 16O 2 have been examined by using a tunable diode laser spectrometer in the region around 12 670 cm - 1 (790 nm). The spectrometer sources are commercially available double heterostructure InGaAlAs tunable diode lasers (TDLs) operating in the “free-running” mode, which allowed the detection of the line positions within 0.01 cm - 1 . The observed carbon dioxide absorption lines belong to the combination overtone 2 ν 2 + 5 ν 3 ro-vibrational band with intensities ranging around 10 - 28 cm / molecule .

High-speed and uncooled operation of 1.3-/spl mu/m InGaAsP strain-compensated MQW BH lasers fabricated on patterned InP substrates

The fabrication and characteristics of 1.3-/spl mu/m InGaAsP strain-compensated multiquantum well (SCMQW) buried heterostructure (BH) laser diodes (LDs) grown by selective metal-organic chemical vapor epitaxy on a patterned InP substrate are demonstrated. The photoluminescence (PL) of the SCMQW active region grown on the patterned grooves has a narrow full-width at half-maximum of /spl sim/ 47 meV. The BH LDs exhibit a threshold current of 6.8 mA, a slope efficiency of 0.45 mW/mA, and a light output power exceeding 30 mW at 80 mA and 20/spl deg/C. The maximum operating temperature is 120/spl deg/C with a characteristic temperature of 72 K in 20/spl deg/C-80/spl deg/C. The 3-dB modulation bandwidth can be extended as far as 11.4 GHz under a bias level of 40 mA, and the back-to-back tests show a clear and symmetric eye diagram at 10 Gb/s with a PRBS of 2/sup 31/-1 word length and a peak-to-peak voltage of 1.08 V at 85/spl deg/C. The average increase in operational current is smaller than 0.84% after the 1500-h aging test. The mean time of the BH LDs operated at 85/spl deg/C to fail is calculated as 9/spl times/10/sup 4/ h. These BH LDs satisfy the reliability requirement for strict loop environment and 10-Gb Ethernet application without special hermetic packaging.

Experimental Study on the Intrinsic Response, Optical and Electrical Parameters of 1.55-$muhboxm$DFB BH Laser Diodes During Aging Tests

This paper reports on an investigation on the light–current, relative intensity noise, and chirp variations of life-tested InGaAsP/InP multiquantum-well buried heterostructure (BH) laser diodes (LDs). The devices have been stressed at highly accelerated aging conditions ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$I = 170 hboxmA$</tex> , <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$T = 140 ^circhboxC$</tex> for 3000 h). Typically, the operating current at constant output optical power <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(I_ op)$</tex> increases logarithmically with time in stable devices while the noise resonance frequency remains stable. High-frequency RF signal-induced chirp for relative stable LDs at constant output power shows very little change with time.

Thermally widely tunable laser diodes with distributed feedback

A thermally widely tunable buried heterostructure laser diode with distributed feedback (DFB) is demonstrated. This device requires only two tuning currents for wide quasicontinuous wavelength tuning, thereby facilitating easy and fast device calibration and control. Furthermore, being based on regular DFB laser fabrication technology, it is readily manufacturable. By using window structures instead of cleaved facets plus antireflection coatings, a regular tuning behavior has been achieved for a DFB-like widely tunable laser diode with only two tuning currents. The laser diode covers the wavelength range between 1552 and 1602 nm. Requiring side-mode suppression ratio and output power above 30 dB and 10 mW, respectively, a wavelength range of 43 nm is accessible.

Direct determination of the free-carrier injection density, the free-carrier absorption, and the recombination factors in double heterostructure diodes by optical phase measurements. Part III

Accurate phase measurements over a temperature interval on double heterostructure laser (DH) diodes provide a means to directly measure the injected free-carrier density and the free-carrier absorption as a function of the injected current. This paper describes the underlying principles and demonstrates the validity of the simple concepts. The data permit to deduce the radiative and nonradiative recombination factors in nominally undoped active layers without taking resource to luminescence measurements. The results presented on GaAs and InGaAsP lattice matched to InP DH diodes show a good overall agreement with calculations based on a heuristic model. The radiative recombination factors at room temperature are near 5.3×10−11 and 2.0×10−11cm3s−1 for GaAs and for InGaAsP with a band gap of 1.122eV, respectively. The free-carrier absorption due to the injected carriers is strongly dispersive and proportional to the 2.3rd power of the wavelength. We show a strong temperature dependence of the free-carrier absorption that is more important in InGaAsP than in GaAs. The results are internally consistent without the need of any free parameter. The phase measurements can also be used to characterize the heat chirping of the active layers under pulsed current excitation.

Properties of InGaN blue laser diodes grown on bulk GaN substrates

High-pressure growth from solution is at present the only method able to provide true bulk GaN monocrystals. In this paper, we would like to demonstrate that in spite of their small, centimeter range size, they can become a technological platform for the realization of high-quality violet and near-UV laser diodes. We used MOVPE technique to deposit InGaN/AlGaN/GaN layers forming a separate confinement heterostructure laser diode. These devices are characterized by a low density of dislocations (∼10 5 cm −2) and a high optical output power of 1.9 W, measured in short pulses (30 ns) to prevent the structure from overheating. We will briefly discuss the challenges we face during the process of optimization of these devices.

InGaAs/AlGaAs Quantum Wire DFB Buried HeteroStructure Laser Diode by One-Time Selective MOCVD on Ridge Substrate

A quasi-buried heterostructure (BH) quantum wire (QWR)-distributed feedback (DFB) laser was realized by one-time selective metalorganic chemical vapor deposition (MOCVD) on a ridge substrate with a submicron grating. One-time selective MOCVD led to the formation of a ridge waveguide with a BH structure and a QWR array for gain-guided DFB laser diode (LD) without additional etching or regrowth process. The threshold current is 15 mA, and the threshold current density is 850 A/cm2. A stable single longitudinal mode was preserved until 3 Ith, after which another mode emerged at a high drive current at 813.6 nm. This suggests a complex-coupled DFB-mode operation. The elimination of the regrowth step enlarges the range of material for extended wavelengths and operational temperatures.

Growth and in situ annealing conditions for long-wavelength (Ga, In)(N, As)/GaAs lasers

The conjugated effect of growth temperature and in situ thermal annealing on the photoluminescence properties of In0.4Ga0.6As0.985N0.015/GaAs quantum wells (QWs) grown by molecular-beam epitaxy has been investigated. The interplay between growth temperature and annealing effects is such as the optimum growth temperature is not the same for as-grown and annealed samples. By using the combination of a low growth temperature and a high in situ annealing temperature, separate confinement heterostructure laser diodes with a single In0.4Ga0.6As1−xNx (x=0.015–0.021)/GaAs QW have been grown. The broad area devices emit from 1.34 to 1.44 μm at room temperature with a threshold current density of 1500–1755A∕cm2.

Influence of the gain saturation on the output performance of quantum-well heterostructures with modified distributed-feedback cavities

Influence of the gain saturation on the output performance of quantum-well heterostructures with modified distributed-feedback cavities is considered. Taking into account symmetrical boundary conditions, distribution of the electromagnetic field in the active region of the heterostructure laser diode with a phase-amplitude grating is determined. It is shown that both the output performance of quantum-well heterostructures and distribution of the electromagnetic field in the active region depend on the pump current and optical nonlinearity characteristics.

Synthesis of AlGaAs-based strained separately confined heterostructure laser diodes by low temperature liquid-phase epitaxy

AlGaAs-based strained separately confined heterostructure laser diodes operating in the 800–900 nm wavelength range have been fabricated from the structures grown using low temperature liquid-phase epitaxy (LPE). Addition of P/Sb to the active region introduces tensile/compressive strain in the structure and is found useful in tuning the emission wavelength. Details of the growth experiments, strain measurements, fabrication and characterization of the laser diodes are described.

Energy band gaps of Zn1−xMgxSySe1−y lattice matched to GaAs

Abstract We report on theoretical study of the energy band gaps for the quaternary alloys Zn1−xMgxSySe1−y in conditions of lattice matching to GaAs substrates using simply the empirical pseudopotential method under the virtual crystal approximation which takes into account the effects of compositional disorder. Our results agree generally very well with the available experimental data. It is shown that the band-gap energies of Zn1−xMgxSySe1−y are expressed by the parabolic function of the composition considering the bowing parameter and that Zn1−xMgxSySe1−y can be a direct or an indirect semiconductor depending on the alloy composition. The Zn0.35Mg0.65S0.6Se0.4 is predicted to meet requirement of the cladding layer for fabricating blue double heterostructure laser diodes using ZnS0.06Se0.94 as the active layer.

Two-mode interference photonic waveguide switch

Based on the two-mode interference principle and the free-carrier plasma dispersion effect, a two-mode interference (TMI) photonic waveguide switch with double carrier injection has been designed and fabricated for application in fiber-optic communications. It consists of an input Y-branch with single-mode ridge waveguides, a TMI waveguide coupling section, and an output Y-branch with single-mode ridge waveguides. The single-mode waveguides and the two-mode waveguide are composed of a SiGe waveguide layer on a Si substrate. The width of the TMI region of the switch is two times that of the single-mode waveguide. On the top of the TMI region and one side of the TMI region, two abrupt p-n junctions are made to inject the carriers into the optical modulation region; on the other side of the TMI region, an abrupt carrier collection region is made to collect the carriers when they are forward biased, so that the double carrier injection photonic waveguide switch has the lowest injection current density. The waveguide layers are made of SiGe/Si material, and the rib waveguides are realized by reactive ion etching. The carrier injection regions and the carrier collection region are formed by ion implantation. The input and output facets of the waveguides were ground and polished by a mechanical method. The switch was characterized by using a 1310-nm InGaAsP/InP heterostructure laser diode. Its insertion loss and ON-state crosstalk were measured to be 2.74 and -15.5 dB, respectively, at a total switching current of 110 mA. The switching time is 180 ns, and the fastest switching time is up to 30 ns.

Collisional broadening and shifting of ammonia absorption lines at 790 nm

By using a diode laser spectrometer based on a commercial heterostructure diode laser operating in free-running mode, line shape parameters of some ammonia ro-vibrational overtones at 790 nm have been measured at room temperature. These weak absorption lines have been detected by using the wavelength modulation spectroscopy technique with second-harmonic detection. The broadening and shifting coefficients have been obtained for ten absorption lines by fitting the collected second-harmonic absorption features and varying the pressure of different buffer gases.

Optimizing HBr ­ Br2 ­ H 2 O Etchants to Form Low Defect Regrowth Interfaces for Highly Reliable InGaAsP/InP Buried-Heterostructure Lasers

We have obtained a tenfold improvement in the reliability of InGaAsP/InP buried heterostructure laser diodes having a dry-etched mesa structure by optimizing the composition of a etchant to produce smooth mesa sidewalls, thus reducing the number of defects at regrowth interfaces. The optimal etchant, which has a composition in the range from 0.30 M HBr/0.022 M to 0.50 M HBr/0.020 M etches both the InP cladding layers and the InGaAsP multi-quantum-well active layer at the same rate. We propose a simple model of the etching process that is consistent with the observed etching characteristics. We found that the etching rate was controlled by the diffusion of molecules, which act as oxidizing agents. © 2003 The Electrochemical Society. All rights reserved.

Contact potential measurement of cleaved mirror surface of 1.3 µm buried heterostructure laser diode by Kelvin probe force microscopy

Contact potential images of a cleaved mirror surface of a 1.3 /spl mu/m buried heterostructure laser diode by Kelvin probe force microscopy have been successfully obtained. The embedded current blocking layer and mesa-etched active region were clearly recognised.

High-gain coupled InGaAs quantum well InAs quantum dot AlGaAs–GaAs–InGaAs–InAs heterostructure diode laser operation

Data are presented showing that a single-layer InAs quantum dot (QD) laser in the AlGaAs–GaAs–InGaAs–InAs heterostructure system is improved in gain and continuous wave (cw) room temperature operation by coupling, via tunneling, auxiliary strained-layer InGaAs quantum wells (QWs) to the single InAs QD layer to assist carrier collection and thermalization. A QW-assisted single-layer InAs QD laser, a QD+QW laser, is demonstrated that operates cw (300 K), and at diode length 150 μm in pulsed operation exhibits gain as high as ∼100 cm−1.

Operation and Catastrophic Optical Degradation of II-VI Laser Diodes at Output Powers larger than 1 W

An output power of 1.55 W, the highest ever reported, at 20 °C has been achieved for a ZnCdSSe/ZnSSe/ZnMgSSe separate-confinement heterostructure laser diode under short-pulsed operation. A differential quantum efficiency of 28% and a maximum conversion efficiency of 1.5% were obtained. The output power was limited by catastrophic optical damage (COD) of the facets, as proved by atomic force microscopy (AFM).

Tunable 3.3 μm InAsSb/InAsSbP diode lasers: a new concept of fast lasing due to nonlinear optical effects

InAsSb/InAsSbP double heterostructure diode lasers for the spectral range of 3.3 μm grown by liquid phase epitaxy have been investigated. Emission spectra, far–field patterns and wavelength tuning versus current have been studied in the wide current range from threshold value I th up to 3 I th at the temperature of liquid nitrogen. Controlled by current, wavelength tuning in single–mode lasing has been obtained both towards the shorter wavelengths (up to 4.56 cm−1) and towards the longer wavelengths (up to 0.9 cm−1) at the temperature T = 77 K. Comparison of the emission properties of the lasers, driven by different types of current (short pulse current, sawtooth pulse current and in quasi–continuous–wave (CW) regime) showed the same quantum–mechanical nature of current tuning. The theoretical model of this nonlinear optical phenomenon is proposed. The estimated times of current tuning defined mainly by the photon lifetime in the cavity are ca. 10−9 to 10−12 s.