GaSb-Based Semiconductor Devices for Optically Pumped Lasers : From saturable absorbers to membrane lasers
Schuchter, Maximilian C. (2025)
Tampere University
2025
Tekniikan ja luonnontieteiden tohtoriohjelma - Doctoral Programme in Engineering and Natural Sciences
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
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Väitöspäivä
2025-10-16
Julkaisun pysyvä osoite on
https://urn.fi/URN:ISBN:978-952-03-4117-6
https://urn.fi/URN:ISBN:978-952-03-4117-6
Tiivistelmä
The short-wave infrared (SWIR, 1.4 - 3 µm) spectral region offers unique advantages for photonic applications in environmental sensing, medical diagnostics, and spectroscopy, overlapping with absorption bands of key trace gases, such as CO2, CH4, and NOx. However, compact and high-performance laser sources in this range remain limited due to challenges in their intrinsic material properties, growth and thermal management capabilities. This dissertation develops and characterizes GaSb-based semiconductor devices, specifically semiconductor saturable absorber mirrors (SESAM), vertical external-cavity surface-emitting laser (VECSEL), and membrane external-cavity surface-emitting laser (MECSEL), engineered for passive modelocking and continuous-wave (cw) operation between 2 - 2.4 µm.
A systematic investigation of GaSb-based SESAMs shows how quantum well (QW) composition, strain, and barrier material can control the recovery dynamics of the SESAMs. Novel GaSbBi SESAMs demonstrated fast interband recovery below 10 ps, reduced two-photon absorption, and low nonsaturable losses, making them promising for high-fluence ultrafast lasers. For high-power emission, GaSb-based MECSELs with strain-optimized InGaAsSb QWs used both in-well and barrier pumping. Silicate bonding to SiC heatspreaders raised processing yield above 60 %. The first barrier-pumped 2.08 µm GaSb MECSEL reached over 2.5 W, with 117 nm in wavelength tunability and no thermal rollover. In-well MECSELs achieved record-low thermal resistance of 0.5 K W−1. Building on this, the first modelocked integrated external-cavity surface-emitting laser (MIXSEL) at 2 µm was realized. Through dispersion engineering and cavity optimization, passive modelocking with clean GHz repetition rates and picosecond pulses was achieved. The spectroscopic potential was shown by measuring CO2 absorption lines in a proof-of-principle dual-comb free-running laser by spatially multiplexing the MIXSEL chip.
This work delivers critical insights into GaSb-based laser materials and device architectures, pushing the performance of compact ultrafast lasers in the SWIR range.
A systematic investigation of GaSb-based SESAMs shows how quantum well (QW) composition, strain, and barrier material can control the recovery dynamics of the SESAMs. Novel GaSbBi SESAMs demonstrated fast interband recovery below 10 ps, reduced two-photon absorption, and low nonsaturable losses, making them promising for high-fluence ultrafast lasers. For high-power emission, GaSb-based MECSELs with strain-optimized InGaAsSb QWs used both in-well and barrier pumping. Silicate bonding to SiC heatspreaders raised processing yield above 60 %. The first barrier-pumped 2.08 µm GaSb MECSEL reached over 2.5 W, with 117 nm in wavelength tunability and no thermal rollover. In-well MECSELs achieved record-low thermal resistance of 0.5 K W−1. Building on this, the first modelocked integrated external-cavity surface-emitting laser (MIXSEL) at 2 µm was realized. Through dispersion engineering and cavity optimization, passive modelocking with clean GHz repetition rates and picosecond pulses was achieved. The spectroscopic potential was shown by measuring CO2 absorption lines in a proof-of-principle dual-comb free-running laser by spatially multiplexing the MIXSEL chip.
This work delivers critical insights into GaSb-based laser materials and device architectures, pushing the performance of compact ultrafast lasers in the SWIR range.
Kokoelmat
- Väitöskirjat [5188]