GaAs-based 1.53 μm GaInNAsSb vertical cavity surface emitting lasers

Electrically-pumped GaAs-based 1.53 mum vertical cavity surface emitting lasers operating in pulsed mode at room temperature and continuous wave (CW) up to 20degC are reported for the first time. The lasers employ a GaInNAsSb/GaNAs multiple quantum well active region, a selectively oxidised AlAs aperture and p- and n-doped Al(Ga)As/GaAs distributed Bragg reflectors. Typical devices have room-temperature pulsed threshold current densities of 8.3 kA/cm and threshold voltages of 5.5 V. CW threshold currents as low as 2.87 mA for a 7 mum aperture device were observed at 15degC.     

IaAsP/InGaAsP quantum-well 1.3 μm vertical-cavity surface-emitting lasers

1.3 μm vertical-cavity surface-emitting lasers based on a novel gain media consisting of InAsP/InGaAsP strain-compensated multiple quantum wells are reported. SiO₂/TiO₂/ dielectric thin-film pairs and wafer-bonded GaAs/Al(Ga)As distributed Bragg reflectors are used as the top and bottom cavity mirrors, respectively. The device with a 5 μm-diameter selectively etched tunnel-junction aperture exhibits submilliampere threshold current as low as 0.54 mA and single-transverse mode emission. Maximum output optical power of 1.9 mW was observed in multimode lasing devices.     

Singlemode emission at 2 μm wavelength with InP based quantum dash DFB lasers

Long wavelength distributed feedback (DFB) laser diodes based on InP quantum dash-in-a-well material have been fabricated and investigated at room temperature under continuous-wave operation. Singlemode emission of InP laser diodes at wavelengths above 2 mum is demonstrated for the first time.     

Room-temperature continuous-wave operation of type-I GaSb-based lasers at 3.1 μm

Type-I interband lasers on GaSb were grown by molecular beam epitaxy using 16 nm InGaAsSb compressively-strained quantum wells (QWs) with 30 nm AlInGaAsSb quinary barriers for improved hole confinement. The 3QW active regions were embedded in standard AlGaAsSb waveguides to limit the thickness of quinary material owing to its low growth temperature requirements. In continuous-wave operation, a typical ridge waveguide laser (width 10 mum, length 1214 mum) produced 6 mW total output power at 20degC with a threshold current of 140 mA. The temperature sensitivity of the devices remains a challenge, as evidenced by the dramatically improved performance at 0degC (16 mW total output power, threshold current 74 mA).     

Relative intensity noise measurements of 5 μm quantum cascade laser and 1.55 μm semiconductor laser

The magnitude of the relative intensity noise (RIN) of a 5 mum distributed-feedback quantum cascade laser (DFB-QCL) was compared with a conventional 1.55 mum DFB laser diode (LD). The RIN for the DFB-QCL at a frequency of 1 MHz was 157 dBm at 10 mW light output, about 5 dB higher than that of the DFB-LD, which could almost be fully explained by the semi-classical noise model. The resonant tunnelling induced noise, which might be a cause of the RIN degradation, was not observed.     

Coupled-defect photonic crystal vertical cavity surface emitting lasers

Photonic crystal patterns containing two defects were fabricated within a large gain area in vertical cavity surface emitting lasers. By designing effective refractive index changes in the region between the defects through cavity shifts caused by photonic crystals, it was possible to coherently couple laser light output from the defects. This enables a novel way to fabricate coherently coupled laser arrays.     

Diode lasers emitting at 3 μm with 300 mW of continuous-wave output power

Type-I double-quantum-well GaSb-based diode lasers operating at 3 mum with room-temperature continuous-wave output power above 300 mW and peak power-conversion efficiency near 8 were designed and fabricated. Laser heterostructure comprised quinary AlGaInAsSb alloy as barrier and waveguide material. Use of quinary alloy resulted in adequate hole confinement. The waveguide thickness was chosen to maximise modal differential gain. Continuous-wave threshold current density about 100 A/cm² per quantum-well and slope efficiency of 100 mW/A were demonstrated at 17degC.     

Singlemode InAs/InP quantum dash distributed feedback lasers emitting in 1.9 μm range

Laterally coupled, complex distributed feedback lasers based on InAs/ InGaAs/InAlGaAs/InP quantum dash-in-a-well layers emitting in the 1.9 mum wavelength range were fabricated. Total CW powers above 25 mW at room temperature and sidemode suppression ratios of more than 35 dB are demonstrated, which makes the devices promising for gas sensing applications.     

Mid-infrared GaSb-based EP-VCSELl emitting at 2.63 μm

Electrically-pumped GaSb-based vertical-cavity surface-emitting lasers emitting up to 2.63 μm at room temperature are reported. The whole structure was grown monolithically in one run by solid-source molecular beam epitaxy. This heterostructure is composed of two n-doped AlAsSb/GaSb DBRs, a type-I GaInAsSb/AlGaAsSb multiquantum- well active region and an InAsSb/GaSb tunnel junction. A quasi-CW (1 μs, 5 %) operation was obtained at room temperature for 35 μm-diameter devices with threshold current of 85 mA.     

GaSb-based monolithic EP-VCSEL emitting above 2.5 μm

The 2 to 3 mm mid-infrared wavelength range is a wellknown transparence window of the atmosphere which contains absorbing lines of numerous polluting gases such as CO, CH/sub 4/, NH/sub 3/ and HF. Currently, one of the more precise gas sensing techniques is tunable diode laser absorption spectroscopy (TDLAS) which measures the absorption of a singlemode laser beam to detect the presence or not of absorbing gases. The realisation of a highly precise trace-gas TDLAS sensing system thus implies the development of specific laser sources exhibiting adapted properties. Electrically-pumped vertical cavity surface emitting lasers (EP-VCSELs) appear particularly well suited to be such laser sources owing to several advantages they offer such as small beam divergence, singlemode operation, fast and far wavelength tunability without mode hops, low threshold, high rate of modulation and less susceptibility to optical feedback [1, 2]. To date, Sb-based heterostructures allow coverage of a major part of the 2 to 4 mm mid-infrared wavelength [3] range. Moreover, recent progress on RT electrically-pumped GaSb-based VCSELs emitting up to 2.3 mm were obtained [4, 5]. However, this wavelength of emission remains the longest ever reported fromany semiconductor EP-VCSELs. In this Letter, the first result of an all-epitaxial monolithic EP-VCSEL emitting at 2.52 mm in quasi-CWregime at room temperature is described.     

InAs/GaSb/InSb short-period super-lattice diode lasers emitting near 3.3 μm at room-temperature

Laser diodes based on 4ML InAs/3ML GaSb/1ML InSb/3ML GaSb short-period superlattices (SPSLs) for emission in the 3?3.5 μm wavelength range have been investigated. Lasing is demonstrated up to 300 K in pulsed conditions and up to 200 K under continuous wave operation. Laser emission is centred at ~3.3 μm, a technologically very important wavelength. The results demonstrate the potential of these new active zones for mid-IR laser diodes.     

Very low threshold current density 1.29 μm GaInNAs triple quantum well lasers grown by MBE

Very low threshold Ga_0.62In_0.38N_0.007As_0.993/GaN_0.011As_0.989/GaAs triple quantum well (QW) lasers emitting at 1.29 mum are demonstrated. The laser structure was grown by molecular beam epitaxy after extensive optimisations of growth and in situ annealing conditions. As- cleaved broad area lasers with a cavity length of 1 mm showed a record low threshold current density of 400 A/cm² (~130 A/cm² / QW), a high differential efficiency of 0.32 W/A/facet and a characteristic temperature of 94 K in the temperature range 10 to 110degC.     

Very-low-threshold current density 1.29 μm GaInNAs triple quantum well lasers grown by molecular beam epitaxy

Very-low-threshold Ga_0.62In_0.38N_0.007As_0.993/GaN_0.011 As_0.989/GaAs triple quantum well (QW) lasers emitting at 1.29 mum are demonstrated. The laser structure was grown by molecular beam epitaxy after extensive optimisations of growth and in situ annealing conditions. As-cleaved broad-area lasers with a cavity length of 1 mm under pulsed operation showed a record low-threshold current density of 400 A/cm² (~130A/cm²/QW), a high differential efficiency of 0.32 W/A/facet and a characteristic temperature of 94 K in the temperature range 10 to 110degC.     

The κ-μ distribution and the η-μ distribution

This paper presents two general fading distributions, the κ-μ and the η-μ distribution, for which fading models are proposed. These distributions are fully characterized in terms of measurable physical parameters. The κ-μ distribution includes the Rice (Nakagami-n), the Nakagami-m, the Rayleigh, and the one-sided Gaussian distributions as special cases. The eta-mu distribution includes the Hoyt (Nakagami-q), the Nakagami-m, the Rayleigh, and the one-sided Gaussian distributions as special cases. Field measurement campaigns were used to validate these distributions. It was observed that their fit to experimental data outperformed that provided by the widely known fading distributions, such as the Rayleigh, Rice, and Nakagami-m. In particular, the κ-μ distribution is better suited for line-of-sight applications, whereas the η-μ distribution gives better results for non-line-of-sight applications     

InP-based short cavity lasers with 2D photonic crystal mirror

The authors have successfully fabricated in-plane emitting InP-based microlasers with cavity lengths of 600-100 μm. The required high reflectivity mirrors consist of a 2D ΓM-oriented triangular photonic crystal of air rods with a lattice constant of 350 nm. The lasers operate CW at room temperature with a threshold current of 29 mA and output power up to 4 mW for the shortest devices     

Ultra-low temperature sensitive deep-well quantum cascade lasers (λ - 4.8 μm) via uptapering conduction band edge of injector region

A new design feature for deep-well quantum cascade (QC) lasers, in which the conduction band edge of the injector region is uptapered, results in virtual suppression of carrier leakage out of the active regions of 4.8 mm emitting devices. For heatsink temperatures in the 20?90°C range the characteristic temperature coefficients for threshold, T₀, and slope efficiency, T₁, reach values as high as 278 and 285 K, respectively, which are nearly twice the values for conventional QC lasers. At 20°C, the threshold current density for uncoated, 30 period, 3 mm-long devices is only ~1.8 kA/cm².     

Uncooled 25 Gbit/s direct modulation of semi-insulating buried-heterostructure 1.3 μm AlGaInAs quantum-well DFB lasers

Uncooled 25 Gbit/s direct modulation of 1.3 mum DFB lasers is demonstrated. The 150 mum-long semi-insulating buried-heterostructure AIGalnAs quantum-well DFB lasers show clear eye-openings with dynamic extinction ratio of 5 dB up to 70degC. 13 km singlemode-fibre transmission experiments using the devices show low power penalty within 1.3 dB between 25 and 70degC. These characteristics are the first achievement by 1.3 mum directly modulated lasers.     

Bandwidth enhancement of injection-locked 1.3 μm quantum-dot DFB laser

Optical injection locking of a quantum-dot distributed-feedback laser at 1.3 mum is reported. Using an injection ratio of 5.3 dB, an optical detuning of -40 pm, and a slave laser biased at 20 mA, the modulation bandwidth of the injection-locked laser was 16.3 GHz. This is over four times higher than the modulation bandwidth of the free-running quantum-dot laser. At a slave laser bias of 5.0 mA, injection locking resulted in a resonance frequency of 21.9 GHz, over eleven times higher than the relaxation frequency of the free-running slave laser.     

High-power InGaAs/GaAs 1.3 μm VCSELS based on novel electrical confinement scheme

Reported are 1.3 mum InGaAs/GaAs vertical-cavity surface-emitting lasers (VCSELs) with a novel electrical confinement scheme based on lithographic definition and selective area epitaxial regrowth in the cavity region. More than 6 mW of output power with a record high differential efficiency of more than 70% is emitted from 10 mum large devices.