J.-M. Lamy

Low temperature p-type doping of (Al)GaN layers using ammonia molecular beam epitaxy for InGaN laser diodes

We demonstrate state-of-the-art p-type (Al)GaN layers deposited at low temperature (740 °C) by ammonia molecular beam epitaxy (NH3-MBE) to be used as top cladding of laser diodes (LDs) with the aim of further reducing the thermal budget on the InGaN quantum well active region. Typical p-type GaN resistivities and contact resistances are 0.4 Ω cm and 5 × 10−4 Ω cm2, respectively. As a test bed, we fabricated a hybrid laser structure emitting at 400 nm combining n-type AlGaN cladding and InGaN active region grown by metal-organic vapor phase epitaxy, with the p-doped waveguide and cladding layers grown by NH3-MBE. Single-mode ridge-waveguide LD exhibits a threshold voltage as low as 4.3 V for an 800 × 2 μm2 ridge dimension and a threshold current density of ∼5 kA cm−2 in continuous wave operation. The series resistance of the device is 6 Ω and the resistivity is 1.5 Ω cm, confirming thereby the excellent electrical properties of p-type Al0.06Ga0.94N:Mg despite the low growth temperature.

Mode locking in monolithic two-section InGaN blue-violet semiconductor lasers

Passive mode-locked pulses with repetition frequencies in the range 40 to 90 GHz were observed in blue-violet GaN-based quantum-well lasers without external cavities. The lasers had two-section geometry with built-in saturable absorber section. The individual pulses had durations as short as 3–5 ps at peak powers of around 320 mW.

Static and dynamic properties of multi-section InGaN-based laser diodes

We have studied multi-section InGaN multiple-quantum-well (MQW) laser diodes grown on c-plane freestanding GaN substrate consisting of an absorber section (AS) and an amplifier gain section. As a result of the interplay between external bias applied to the AS and the internal piezoelectric and spontaneous polarization fields inherent to c-plane InGaN MQWs, the devices exhibit non-linear non-monotonic variations of the threshold current due to the quantum-confined Stark effect that takes place in the AS MQWs. We report on how this effect tailors the lasing characteristics and lasing dynamics, leading from a steady-state cw lasing regime for an unbiased AS to self-pulsation and Q-switching regimes at high negative absorber bias.

InGaN laser diodes emitting at 500 nm with p-layers grown by molecular beam epitaxy

We demonstrate hybrid laser diodes by combining n-type layers and an active region grown by metal organic vapor phase epitaxy with p-type layers grown by molecular beam epitaxy. These p-doped layers, grown at 740 degrees C, exhibit state-of-the-art electrical characteristics and prevent the indium-rich quantum wells from thermal degradation. Narrow ridge-waveguide lasers with high-reflectivity coatings show a threshold current density of 9.7 kA.cm(-2), a threshold voltage of 5.4V, and a lasing wavelength of 501 nm. The internal optical loss and material gain of the epitaxial structures are also measured and discussed

Solitary pulse-on-demand production by optical injection locking of passively Q-switched InGaN diode laser near lasing threshold

We report on optical injection locking of Q-switched InGaN multi-section diode laser from CW tunable laser to produce solitary pulses at precise wavelength. To the best of our knowledge, this has never been done before.

Passive mode-locking in the cavity of monolithic GaN-based multi-section laser diodes

We demonstrate picosecond pulse generation in the blue-violet wavelength region by passive intra-cavity mode-locking in GaN-based ridge waveguide laser diodes with monolithically integrated absorbers. For cavity lengths of 1.2 and 0.6 mm we observe repetition frequencies of 40 and 90 GHz, and pulse lengths of 7 and 4 ps, respectively. The results are explained by an extremely short, tunneling dominated carrier life time in the saturable absorber at high negative bias. The fast depletion of the charge carriers in the absorber is investigated by bias-dependent life-time measurements in the absorber.

Solitary Pulse-on-Demand Production by Optical Injection Locking of Passively Q-Switched InGaN Diode Lasers Near Lasing Threshold

We report on optical injection locking of Q-switched InGaN multi-section diode laser from CW tunable laser to produce solitary pulses at precise wavelength. To the best of our knowledge, this has never been done before.

Superfluorescent 1.1 ps pulse-on-demand generation in InGaN laser

A semiconductor laser diode producing ultra-short optical pulses in the blue-violet range will find numerous applications ranging from next-generation 3D optical data storage devices to bio-medical diagnostic methods. In this communication we report generation of solitary pulses of the width below 1.1 ps from a tandem-cavity InGaN/InGaN laser diodes operating in 415-425 nm wavelength range. Solitary pulses are produced in the pulse-on-demand mode within narrow transient region between amplified spontaneous emission (ASE) and Q-switched lasing (LAS). The pulses exhibit large jitter. This regime is achieved when high negative bias -20 V was applied to the central section of the device (saturable electroabsorber) while to end sections were pumped with 1 A current pulses.

Passive and hybrid mode-locking from a monolithic InGaN/GaN laser diode

We report 4ps and 8ps pulse generation from a two-section monolithic InGaN/GaN laser by hybrid and passive mode-locking, respectively. Pulse trains at a repetition rate of 28.6GHz and an emission wavelength of 422nm are generated.

Effect of applied bias voltage on the static and dynamic characteristics of self-pulsating multi-section InGaN-based laser diode

InGaN-based laser diodes (LDs) are suitable for obtaining low-cost and compact short-pulse laser light sources in the blue-violet range exploiting either mode-locking or self-pulsating regimes. Typically these devices consist of a Fabry-Perot-type cavity with separate electrical p-contacts to define multiple sections: a short reverse-biased section that acts as a saturable absorber (SA) and a long forward-biased gain section. Recently we demonstrated 18 ps duration optical pulses under the self-pulsation regime on InGaN multi-section blue LDs at repetition rate of several GHz [1]. The development of this new kind of ultrafast sources would be of great interest for applications such as next generation large-capacity optical storage, ultraprecise nano-processing and biomedical imaging [2].