Quantum-dot Edge-emitting Laser Research Articles

Integration of Edge-Emitting Quantum Dot Lasers with Different Waveguide Platforms using Micro-Transfer Printing

O-band InAs/GaAs Quantum Dot edge-emitting lasers are integrated onto a number of waveguiding platforms using micro-transfer printing. These are deep recesses in 220 nm Si, 3 µm Si and 300 nm SiN waveguide circuits. The processing technology to achieve release and high-yield accurate transfer of laser coupons up to 2.4 mm long and < 5 µm thick onto the target substrates is described. At 85 mA, waveguide coupled powers of 1.0 mW and 0.95 mW are measured after out-coupling from the 220 nm SOI and 300 nm SiN waveguides, respectively while 1.7 mW total power was measured from the 3 µm SOI waveguide.

Optimization of 1.55 μm quantum dot edge-emitting lasers for narrow spectral linewidth

Quantum dots are well known as active laser materials with remarkable properties such as high differential gain, low linewidth enhancement factor and low threshold current density. In this paper we use a comprehensive traveling wave based laser model to investigate the spectral linewidth of quantum dot edge-emitting lasers for use in high bit rate optical communications. By systematic optimization of the resonant cavity design we reach linewidths of below 10 kHz, which is a reduction by an order of magnitude compared to classical distributed feedback laser designs.

Optimization of the design and mode of operation of a QD laser for reducing the heat-to-bitrate ratio

Heat dissipation under the high-speed modulation of quantum dot edge-emitting lasers is considered. It is shown that, for a given laser diode, there is a bias current at which the heat-to-bitrate ratio is minimized. Moreover, there exists a certain optimal optical loss of the laser cavity at which the lowest heat-to-bitrate ratio is provided for any design of edge-emitting lasers that can be fabricated from an epitaxial structure. The heat-to-bitrate ratio and the corresponding bitrate are numerically calculated and analytical expressions are derived. It is demonstrated that the heat-to-bitrate ratio of quantum dot edge-emitting lasers can be less than 0.4 pJ/bit at a bitrate exceeding 10 Gbit/s.

High-Power Versatile Picosecond Pulse Generation from Mode-Locked Quantum-Dot Laser Diodes

This paper presents the current status of our research in mode-locked quantum-dot edge-emitting laser diodes, particularly highlighting the recent progress in spectral and temporal versatility of both monolithic and external-cavity laser configurations. Spectral versatility is demonstrated through broadband tunability and novel mode-locking regimes that involve distinct spectral bands, such as dual-wavelength mode-locking, and robust high-power wavelength bistability. Broad tunability of the pulse repetition rate is also demonstrated for an external-cavity mode-locked quantum-dot laser, revealing a nearly constant pulse peak power at different pulse repetition rates. High-energy and low-noise pulse generations are demonstrated for low-pulse repetition rates. These recent advances confirm the potential of quantum-dot lasers as versatile, compact, and low-cost sources of ultrashort pulses.

Bistability and opto-thermal-pulsations in a quantum-dot edge-emitting laser diode

Self-sustained pulsations in the output of an InAs quantum dot laser diode in the MHz range are reported for the first time. The characteristics (shape, range and frequency) are presented for the free running laser and when optical feedback in the Littrow configuration is applied. The time scale suggest that these are opto-thermal pulsation similar to those reported in quantum well amplifiers. Bistability in the light-current characteristics is observed for wavelengths smaller the gain peak (λ = 1225 nm), but it is not present for wavelength above the gain peak and for the free running lasers.

Investigation of transition dynamics in a quantum-dot laser optically pumped by femtosecond pulses

The behavior of a quantum-dot edge-emitting laser, optically pumped by femtosecond pulses, has been investigated. It has been observed that pulses generated by the laser from ground-state transitions have longer durations than those generated from the excited states. Interestingly, the shortest pulses were generated when the transitions from the first excited-state were dominant.

Room-temperature operation of patterned quantum-dot lasers fabricated by electron beam lithography and selective area metal-organic chemical vapor deposition

We have developed a quantum-dot fabrication process which allows for explicit definition of the location and lateral dimension of quantum dots using electron beam lithography and selective area metal-organic chemical vapor deposition. We have demonstrated the first reported room-temperature operation of a patterned quantum-dot edge-emitting laser based on this fabrication technique.

EXTENDED WAVELENGTH (1.0 to 1.3 μm) InGaAs/GaAs QUANTUM DOT GaAs-BASED VERTICAL-CAVITY SURFACE-EMITTING AND LATERAL-CAVITY EDGE-EMITTING LASERS

An important advance in InGaAs/GaAs quantum dot lasers has been the demonstration of lasing at wavelengths significantly longer than that possible using InGaAs strained quantum wells, extending beyond 1.3 μm. These fully GaAs-based active regions are compatible with commercial vertical-cavity surface-emitting laser (VCSEL) technology based on selective oxidation, and offer novel performance due to their three-dimensional electronic confinement. This chapter reviews the status of long wavelength quantum dot edge-emitting lasers and VCSELs, and presents some of the new physical principles needed to understand their novel device characteristics.