Μm Laser Diode Research Articles

Effect of symmetric and asymmetric In0.2Ga0.8As wells on the structural and optical properties of InAs quantum dots grown by migration enhanced molecular beam epitaxy for the application to a 1.3 μm laser diode

In this article, we present an in-depth study of the effects of the structural and optical properties of InAs “dots in an In0.2Ga0.8As well” (DWELL) and InAs “dots in an asymmetric In0.2Ga0.8As well” (asym. DWELL) grown by migration-enhanced molecular beam epitaxy. The energy spacing (ΔE1) between the ground-state and the first-excited-state transitions increases from 66 meV for the DWELL to 73 meV for the asym. DWELL. These results are consistent with ΔE1 measured by photoluminescence excitation and the values of activation energy fitting. The photoluminescence linewidth of the asym. DWELL (40 meV) is narrower than that of the DWELL (70 meV), which shows superior uniformity in the former over the latter. The trends of the properties of the DWELL and the asym. DWELL deduced from the structural properties are in good agreement with those from the optical properties. From the results, it is strongly supported that the asym. DWELL is more suitable for application to long wavelength optical communication than the DWELL counterpart.

Near infrared absorption and room temperature photovoltaic response in AlN∕GaN superlattices grown by metal-organic vapor-phase epitaxy

We report on intersubband absorption of near infrared radiation in AlN∕GaN superlattice structures grown by metal-organic vapor-phase epitaxy. A good correlation between well thickness and absorption peak energy was obtained. One sample shows a photovoltaic signal which overlaps well with the corresponding absorption curve at around 1.5μm (830meV), a common wavelength in optical fiber telecommunication systems. This photovoltaic signal is strongest at temperatures around 75K and persists up to room temperature. The frequency response of this sample was measured with a modulated 1.5μm laser diode. The amplitude of the response was highest for a frequency of 36kHz.

Fabrication and characterization of a spot-size converter-integrated 1.3 µm FP laser diode

We fabricated a spot-size converter-integrated 1.3 µm laser diode with a conventional buried-heterostructure laser process. For the spot-size converter, we employed a double-waveguide structure in which a ridge-based passive waveguide was incorporated. The passive waveguide was optically combined with a laterally tapered active waveguide to control the mode size. The device showed a low threshold current of 6.5 mA and high slope efficiency of 0.29 W A−1. The beam divergences in horizontal and vertical directions were 6.1° and 15.7°, respectively. A minimum coupling loss was 3.7 dB and the alignment tolerance with the additional 1 dB loss was ±2.4 µm for horizontal and ±1.7 µm for vertical directions. The 3 dB modulation bandwidth was 4.8–6.8 GHz with the operation current between 40 mA and 100 mA. We obtained clear open eye patterns at 1.25 Gbps operation.

Self-activated Nd3+:Ba2NaNb5O12 optical super-lattices: Micro characterization and non-collinear laser light generation

Czochralsky grown Nd3+-ion doped barium sodium niobate (Ba2NaNb5O12, “banana”) optical super-lattices have been characterized by a combination of chemical etching, optical microscopy, micro-Raman and micro-photoluminescence experiments. The presence of ferroelectric domains, induced during growth process, is accompanied by a periodic modulation of Nd3+-ion concentration as well as by a small lattice distortion. When Nd3+-ion laser action at ≈1.06μm is achieved under 0.808μm laser diode pumping, the singularities of refractive index caused by opposed ferroelectric domains lead to non-collinear intra-cavity propagation.

Molecular beam epitaxy growth of quantum dot lasers emitting around 1.5 μm on InP(3 1 1)B substrates

We present a modified growth procedure used to control the emission wavelength of InAs quantum dots in a GaInAsP matrix grown on InP(3 1 1)B substrates by gas source molecular beam epitaxy. In this procedure, the quantum dots are grown on a GaInAsP buffer layer and partially capped with the same GaInAsp alloy. Then As/P exchanges during a growth interruption are used in order to reduce quantum dots height and thus to control the emission wavelength. Two GaInAsP quaternary alloys composition have been studied in this work. Both could be used as optical waveguide in 1.55 μm laser diodes. We present and compare photoluminescence results on test structures with these two quaternary alloys. Finally, the new growth procedure is successfully applied and we demonstrate a quantum dot laser emission at 1.58–1.61 μm at 300 K.

1.55 µm spot-size converter with monolithically integrated laser diode by conventional process

A novel 1.55 µm laser diode (LD) with monolithically integrated spot-size converter (SSC) is designed and fabricated using conventional photolithography and the chemical wet etching process. For the laser diode, a ridge double-core structure is employed. For the spot-size converter, a buried double-waveguide structure is incorporated. The laterally tapered active core is designed and optically combined with the thin passive core to control the size of the mode. The threshold current was measured to be 40 mA together with high slope efficiency of 0.35 W A−1. The beam divergence angles in the horizontal and vertical directions were as small as 14.9° and 18.2°, respectively.

Sensitive in situ detection of CO and O 2 in a rotary kiln-based hazardous waste incinerator using 760 nm and new 2.3 μm diode lasers

CO and O 2 are key combustion parameters closely linked to the process stoichiometry and most frequently determined by gas sampling. This limits time resolution and hinders the extraction of representative concentration data from inhomogeneous flue gas streams. Especially, batch-fired processes like hazardous waste incineration in rotary kilns (RK) face fast and spatially confined CO fluctuations, making them difficult to optimize. To address this sensor deficiency, we used new 2.3 μm distributed-feedback diode lasers (DFB-DL) accessing the CO-2 ν-band to develop fast, sensitive, and spatially integrating in situ absorption spectrometers suitable for the harsh conditions in full-scale combustion processes. Spectrally multiplexing the 2.3 μm-DL with a 760 nm-DFB-DL for the O 2-A-band we also developed a simultaneous in situ CO/O 2 spectrometer, which is most interesting for control strategies requiring the coverage of wide stoichiometry ranges. These new spectrometers were successfully tested for up to two weeks in a 3.5 MW th hazardous waste incinerator. The absorption path ( l = 2.56 m, T = 800–1000 °C) was located in the post-combustion chamber right at the RK exit. Direct absorption spectroscopy enabled calibration-free species detection. A new data acquisition system using a digital signal processor and voltage-controlled preamplifiers ensured 100% data throughput, enabled a real-time validity and transmission evaluation of individual laser scans, and thus permitted a real-time transmission compensation and hence an automatic dynamic range adaptation. This proved to be an effective method to avoid systematic errors found in PC-based systems under these rapidly fluctuating combustion conditions. With 1 s acquisition time we achieved for CO/O 2 an optical resolution (1 σ) of 1.2 × 10 −4/6 × 10 −5 OD corresponding to detection limits of 6.5 ppm CO and 250 ppm O 2. Sensitivity and time resolution of the spectrometer was high enough to detect—even under fuel lean conditions—small periodic stoichiometry and CO changes caused by the periodic fuel feed of the RK.

Double resonance optical pumping spectrum and its application for frequency stabilization of a laser diode

We present double resonance optical pumping (DROP) spectra for the 5P3∕2–4D3∕2 transition and the 5P3∕2–4D5∕2 transition of R87b and we use these spectra for frequency stabilization in the 1.5μm region. The spectra, compared to the conventional double resonance spectrum, show a good signal-to-noise ratio and a narrow spectral linewidth for laser frequency stabilization. The different intensities of the hyperfine states were attributed to the different rates of double resonance optical pumping into the other ground state. When we stabilized the frequency of a 1.5μm laser diode to the DROP spectrum, the best frequency stability was 1×10−11 after 100s.

Design and fabrication of thermal actuators used for a micro-optical bench: application to a tunable Fabry-Perot filter

Recent studies of MEMS thermal micro-actuators have shown that simple devices can provide deflection on the order of 10 μm at low voltages. These thermo-mechanical devices operate by differential thermal expansion caused by ohmic heating in the U-shaped beam of the device. We report on a thermal actuator based on asymmetrical thermal expansion of two beams caused by ohmic heating. Because of the intervention of the different heat transfert mode (such as conduction, convection, and radiation), the motion simulation can be complex. This work demonstrates a good comprehension of the phenomena during a Joule heating process for micro-systems and the development of an analytical model and a finite element analysis. Comparisons between theory and experimental results validate the steady-state conditions. Therefore, this actuator has been successfully integrated in an optical bench and allows the displacement of a micro-lens supported by a movable silicon-frame. This optical bench has been tested to realize a tunable Fabry-Perot filter with a 0.8 μm laser diode and reflective mirror of 99%.

Space applications of optical communications

Optical communication in Space is now a reality. In this paper we present the recent developments that were undertaken in Europe for this application. We first describe the different missions where optical communications are useful: link between two geostationary satellites (geo-geo), Data Relay Mission (leo-geo) and High Data Rate Satellite Constellation Network. Then we detail the different candidate laser technologies from the most straightforward technologies that have been developed for optical fiber applications (λ=1.55 µm) and 0.8 µm technology based on Silicon detector to the recent developments based on high power fiber amplifiers. In the last chapter we describe thesilex (Semi conductor Intersatellite Link Experiment) program which performs optical communication betweenspot4 Earth observation satellite (cnes) andartemis (esa). The excellent results based on 0.8 µm laser diode technology are considered to be a major milestone in optical intersatellite communication

Impact of 1.55 μm laser diode degradation laws on fibre optic system performances using a system simulator

Impact of 1.55 μm laser diode degradation laws on fibre optic system performances using a system simulator

GaSb-based mid-infrared 2–5 μm laser diodes

Laser diodes emitting at room temperature in continuous wave regime (CW) in the mid-infrared (2–5 μm spectral domain) are needed for applications such as high sensitivity gas analysis by tunable diode laser absorption spectroscopy (TDLAS) and environmental monitoring. Such semiconductor devices do not exist today, with the exception of type-I GaInAsSb/AlGaAsSb quantum well laser diodes which show excellent room temperature performance, but only in the 2.0–2.6 μm wavelength range. Beyond 2.6 μm, type-II GaInAsSb/GaSb QW lasers, type-III ‘W’ InAs/GaInSb lasers, and interband quantum cascade lasers employing the InAs/Ga(In)Sb/AlSb system, all based on GaSb substrate, are competitive technologies to reach the goal of room temperature CW operation. These different technologies are discussed in this paper. To cite this article: A. Joullié, P. Christol, C. R. Physique 4 (2003).

Application of InAsSb/InAsSbP and lead chalcogenide infrared diode lasers for photoacoustic detection in the 3.2 and 5 μm region

An investigation of photoacoustic detection using 3.2–3.6 and 5 μm diode lasers is described. An inexpensive resonant photoacoustic system was developed based, on a simple glass cell and condenser and electret microphone (Brüel & Kjaer type 4144/Sennheiser type K6P). The system was tested on the single rotation–vibration lines of C 2H 2, CO, COS, and NH 3 gases. The best detection limits obtained are 300 ppm V for C 2H 2 and 20 ppm V for COS. Potential applications of infrared diode laser photoacoustic detection lie in the areas of analytical chemistry, atmospheric research, and investigation of the kinetics of reactive species.

Low-threshold-current 1.2–1.5 μm laser diodes based on AlInGaAs/InP heterostructures

Separate confinement AlInGaAs/InP multiwell laser heterostructures emitting in a wavelength range of 1.2–1.5 μm have been synthesized by metalorganic vapor-phase epitaxy. The threshold current of laser diodes with a strip width of 4.5μm and a cavity length of 200μm was as low as 10 mA. With a cavity length of 1.0 mm, the threshold current density was 500–650 A/cm2. The laser diodes can operate in a continuous regime without forced cooling at an ambient temperature of up to 170°C. In a temperature range from 10 to 80°C, the characteristic temperature parameter T0 reached up to 110 K.

Site-selective nitrogen isotopic ratio measurement of nitrous oxide using 2 μm diode lasers

We demonstrate a high-precision measurement of the isotopomer abundance ratio 14N 15N 16O/ 15N 14N 16O/ 14N 14N 16O (≈0.37/0.37/100) using three wavelength-modulated 2 μm diode lasers combined with a multipass cell which provides different optical pathlengths of 100 and 1 m to compensate the large abundance difference. A set of absorption lines for which the absorbances have almost the same temperature dependence are selected so that the effect of a change in gas temperature is minimized. The test experiment using pure nearly natural-abundance N 2O samples showed that the site-selective 15N/ 14N ratios can be measured relative to a reference material with a precision of ±3×10 −4 (±0.3‰) in ≈2 h.

Nitrogen-plasma study for plasma-assisted MBE growth of 1.3 μm laser diodes

We have studied the influence of radio-frequency plasma cell operating conditions on the plasma-assisted molecular-beam epitaxy growth of bulk GaAsN and GaInAsN quantum wells. For low N 2 flow rates, the species that mostly incorporate are atoms and the dissociation fraction of N 2 for the lowest flow rate and the highest RF power has been found to be up to 0.7. For high N 2 flow rates, the species that mostly incorporate are vibrationally excited molecules in the N 2( X, v) ground state. The vibrational temperature of the N 2( X, v) ground state has been found to be higher than 10 4 K. The ion damage has been decreased by increasing the N 2 pressure which induces a decrease of the electron temperature and consequently a decrease of the plasma ionization. Oxygen has been evidenced to incorporate proportionally to nitrogen and its emission line has been identified in the plasma emission spectrum. Finally, quantum-well structures emitting at around 1.3 μm at 300 K have been fabricated and characterized by photoluminescence and photocurrent spectroscopy.

High power single-mode (λ=1.3–1.6 μm) laser diodes based on quantum well InGaAsP/InP heterostructures

The possibility of achieving maximal optical output power in the single-mode lasing for mesa-stripe laser diodes fabricated on the basis of InGaAsP/InP quantum-well heterostructures with separate confinement have been studied both experimentally and theoretically. The basic condition for the single-mode lasing of laser diodes in a wide range of driving currents is shown to be the precise choice of the effective refractive index ΔnL discontinuity in the plane parallel to the p-n junction. A InGaAsP/InP separate confinement heterostructure with a step waveguide, with a threshold current density of 180 A/cm2 and an internal quantum efficiency of stimulated emission of 93–99%, has been manufactured via the MOCVD method. The optimization of the mesa-stripe diode design for the developed InGaAsP/InP heterostructure is carried out with the aim of achieving maximal optical output power in the case of single-mode lasing. An output power of 185 mW is attained in the laser diode with the mesa-stripe width W=4.5 μm (λ=1480 nm). The maximal continuous output power was as high as 300 mW. The full width at half-maximum (FWHM) of the lateral far-field pattern increased by 1° relative to the threshold value.

Comprehensive modeling of the electro-optical-thermal behavior of (AlGaIn)(AsSb)-based 2.0 μm diode lasers

Strained triple-quantum-well, large-optical-cavity GaInSb/AlGaAsSb/GaSb diode lasers emitting at 1.98 μm at 300 K are investigated with regard to their high-power capability. As the heating of the active region is a limiting factor for these devices, a quantitative model is derived to simulate the performance of these lasers including thermal effects. The standard laser parameters, deduced from measurements on ridge waveguide lasers, and the measured thermal resistance of the mounted devices were then taken as input parameters. The output power and power efficiency of the lasers calculated using the presented model. Good agreement was found between calculated data and the measurements for different heatsink temperatures as well as for different laser geometries and mounting techniques. The maximum output power achieved for p-side down mounted 1000×150 μm2 broad-area laser was 1.7 W at 300 K in cw operation.

Molecular beam epitaxial growth of GaAs 1− XN X with dispersive nitrogen source

The great bowing parameter of GaAsN makes this material hopeful for the fabrication of 1.3 and 1.55 μm laser diodes and detectors. However, the effect of energetic nitrogen ion bombardment during growth may have a deleterious effect on the material quality. To avoid the bombardment effect of energetic nitrogen ions, a modified mode for GaAsN growth using dispersive nitrogen is reported. High-quality GaAsN epilayers and abrupt GaAsN/GaAs interfaces were demonstrated using this growth mode. For the first time, a GaAsN/GaAs double quantum well sample was grown with dispersive nitrogen source. Under our annealing conditions of 750°C from 10 s to 10 min, no significant evidence of nitrogen out-diffusion from the material was found. The improvement in optical quality due to annealing is attributed to the annihilation of nitrogen-related defects through atomic rearrangement of the lattice, the effect of which on the observed blueshift in the photoluminescence peak needs further investigation.

First successful growth of TlInGaAs layers on GaAs substrates by gas source MBE

To realize the temperature-stable threshold-current and lasing-wavelength 1.3–1.5 μm laser diodes, TlInGaAsN/AlGaAs heterostructures were proposed. As a first step, TlInGaAs was successfully grown, for the first time, on GaAs substrate by molecular beam epitaxy. The incorporation of Tl was confirmed with reflection high-energy electron diffraction intensity oscillation measurement. Photoluminescence (PL) measurements were conducted on the TlInGaAs/GaAs and InGaAs/GaAs heterostructure samples and the red shift of the PL peak energy was observed for the TlInGaAs/GaAs samples, as expected.