Orientation-patterned waveguides for tunable mid-infrared GaSb laser diodes – Great GaSby

Solid-state and semiconductor laser sources suited to mid-infrared (MIR) emission, from 2 to 12 µm, have witnessed tremendous progress during the past years with the respective advent of user-friendly non-linear wavelength converting crystals based on Quasi-Phase Matching (QPM), antimonide (GaSb) diode lasers and Quantum Cascade Lasers (QCL). Nevertheless, none of these technologies alone is able to provide the widely-tunable, affordable and compact source which is needed for IR applications as varied as spectroscopy, material processing, medical lasers and military and civilian counter-measures. The Great GaSby project aims at filling this gap by capitalizing on the recent progress in both GaSb laser diodes and QPM-based wavelength conversion in Orientation-Patterned (OP) III-V semiconductors.

GaSb-based laser diodes have been under development for a couple of decades now and they reach a certain level of maturity in the wavelength region around 2 µm where CW operation with low threshold current and output power around 1 W has been demonstrated. IES is a leader in this field. In parallel, non-linear frequency conversion has witnessed an unprecedented leap with regard to both versatility and affordability allowing demonstrating efficient QPM wavelength conversion of various CW or pulsed lasers. Recently, optical-parametric oscillation has been demonstrated by optical pumping of Orientation-Patterned GaAs (OP-GaAs) where the change in output wavelength can be obtained by varying either the QPM period, the temperature or the pumping wavelength. III-V Lab and TRT are leaders in this field.

The Great GaSby project aims at the highly ambitious demonstration of electrically-pumped optical parametric oscillation in orientation-patterned III-Sb waveguides thanks to GaSb laser diodes co-integrated with OP-GaSb waveguides. The joint implementation of III-Sb active structures emitting in the 2.0 – 2.5 µm wavelength range and OP-GaSb waveguides efficiently converting this pump in the 2.5 – 12 µm wavelength range will offer a perfect match toward electrically-pumped monolithic semiconductor lasers sources with an unprecedented tuning capability.

Key motivations behind this concept include:
• an obviously increased efficiency when pumping at 2 µm as compared to 1 µm for OPO emission, both in the poorly addressed 3 µm window and in the fingerprint region (above 6 µm), most relevant for spectroscopy applications,
• an ideal match to the specifications for band II counter-measures for defence applications,
• a protection against detrimental two-photon absorption effects which occurs in GaAs,
• the benefit from a second-order susceptibility of GaSb about 50% superior to GaAs.

Besides management and valorization, the main tasks of the workplan of the project are :
1) Hetero-Epitaxy based OP-waveguides: MBE growth of OP-GaSb layers on OP-GaAs templates. This takes advantage of the well-established fabrication process for OP-GaAs templates. The novelty of this development will be to grow a GaSb buffer suited to further growth of high quality guiding layers and ridges preserving the designed orientation-patterning in spite of strain-relaxation defects.
2) Homo-Epitaxy based OP-waveguides: OP-GaSb templates will be produced by wafer bonding and the targeted OP-GaSb structures will be homoepitaxially grown on these templates. This approach will benefit from a low defect density whereas the main hard point is the template preparation.
3) Active structures: GaSb-laser diodes emitting near 2 µm will be co-integrated with the OP-GaSb waveguide for mid-IR conversion. Two different approaches have been derived to mitigate the risk.

To the best of our knowledge, the growth on OP-GaSb templates is completely new whereas electrically-pumped OPO in orientation-patterned III-V waveguides has never been demonstrated.