Soile Suomalainen

Harmonically mode-locked VECSELs for multi-GHz pulse train generation

We report on optically-pumped vertical-external-cavity surface-emitting lasers passively mode-locked with a semiconductor saturable-absorber mirror. The potential of harmonic mode-locking in producing pulse trains at multigigahertz repetition rates has been explored. The results present first systematic study of multiple pulse formation in passively mode-locked VECSELs.

Broadband semiconductor saturable absorber mirrors in the 1.55-/spl mu/m wavelength range for pulse generation in fiber lasers

Broadband low-loss semiconductor saturable absorber mirrors (SESAMs) in the 1.55-/spl mu/m wavelength range were monolithically grown by solid source molecular beam epitaxy using a Burstein-Moss blue-shifted Ga/sub 0.47/In/sub 0.53/As-InP distributed Bragg reflector. Absorbers with fast and slow temporal responses were used to start up and to stabilize a stretched pulse mode-locked fiber laser. Reliable operation at a fundamental repetition rate was obtained without multiple pulse break-up with pulse energy of over 250 pJ.

Long-wavelength fast semiconductor saturable absorber mirrors using metamorphic growth on GaAs substrates

Metamorphic growth of InP on GaAs has been used to decrease the absorption recovery time of 1.55μm semiconductor saturable absorber mirrors. We show that the recovery time can be reliably controlled by changing the thickness of an InP “lattice reformation layer” grown between the GaAs-based distributed Bragg reflector and the active region. Semiconductor saturable absorber mirrors with a thickness of the InP reformation layer around 200 nm or smaller exhibit a recovery time short enough to reliably mode-lock fiber lasers.

Mode-locking of 2 μm Tm,Ho:YAG laser with GaInAs and GaSb-based SESAMs

We have investigated passive mode-locking of Tm,Ho:YAG lasers with GaInAs- and GaSb-based semiconductor saturable absorber mirrors (SESAMs). With a GaInAs-based SESAM, stable dual-wavelength mode-locking operation was achieved at 2091 nm and 2097 nm, generating pulses with duration of 56.9 ps and a maximum output power of 285 mW. By using the GaSb-based SESAMs, we could generate mode-locked pulses as short as 21.3 ps at 2091 nm with a maximum output power of 63 mW. We attribute the shorter pulse duration obtained with the GaSb SESAMs to the ultrafast recovery time of the absorption and higher nonlinearity compared to standard GaInAs SESAMs.

Picosecond passively mode-locked GaSb-based semiconductor disk laser operating at 2μm

We report on a passively mode-locked optically pumped GaSb-based semiconductor disk laser producing stable picosecond optical pulses at a 1.95 μm wavelength. The gain mirror was comprised of a 15 quantum well InGaSb/GaSb structure. A fast semiconductor saturable absorber mirror with three InGaSb/GaSb quantum wells was used to attain self-starting mode-locked operation at a fundamental repetition rate of 881.2 MHz. The laser produced pulses with 30 pJ energy and a duration of 1.1 ps within a factor of 2 of the Fourier limit.

Power scalable semiconductor disk laser using multiple gain cavity

We report on power scaling of optically-pumped semiconductor disk laser using multiple gain scheme. Increased power and threshold of rollover have been achieved in dual-gain configuration owing to reduced thermal load for each gain element.

GaSb-based SESAM mode-locked Tm:YAG ceramic laser at 2 µm

Tunable and mode-locked laser operation near 2 µm based on different Tm-doped YAG ceramics, 4 at.% and 10 at.%, is demonstrated. Several designs of GaSb-based surface-quantum-well SESAMs are characterized and studied as saturable absorbers for mode-locking. Best mode-locking performance was achieved using an antireflection-coated near-surface quantum-well SESAM, resulting in a pulse duration of ~3 ps and ~150 mW average output power at 89 MHz. All mode-locked Tm:YAG ceramic lasers operated at 2012 nm, with over 133 nm demonstrated tuning for continuous-wave operation.

Spectral narrowing and locking of a vertical-external-cavity surface-emitting laser using an intracavity volume Bragg grating

We report the use of a volume Bragg grating as an output coupler mirror to improve and stabilize the spectral characteristics of 1058-nm vertical-external-cavity surface-emitting laser which is thermally managed using an intracavity diamond heatspreader. Spectrally narrow and locked emission with up to 645mW of TEM0,0 output power is demonstrated

Semiconductor Disk Lasers: Recent Advances in Generation of Yellow-Orange and Mid-IR Radiation

We review the recent advances in the development of semiconductor disk lasers (SDLs) producing yellow-orange and mid-IR radiation. In particular, we focus on presenting the fabrication challenges and characteristics of high-power GaInNAs- and GaSb-based gain mirrors. These two material systems have recently sparked a new wave of interest in developing SDLs for high-impact applications in medicine, spectroscopy, or astronomy. The dilute nitride (GaInNAs) gain mirrors enable emission of more than 11 W of output power at a wavelength range of 1180–1200 nm and subsequent intracavity frequency doubling to generate yellow-orange radiation with power exceeding 7 W. The GaSb gain mirrors have been used to leverage the advantages offered by SDLs to the 2–3 μm wavelength range. Most recently, GaSb-based SDLs incorporating semiconductor saturable absorber mirrors were used to generate optical pulses as short as 384 fs at 2 μm, the shortest pulses obtained from a semiconductor laser at this wavelength range.

SESAM mode-locked Tm:CALGO laser at 2 µm

GaSb-based SESAM is successfully employed for passive mode locking of a Tm3+:CaGdAlO4 laser operating near 2 µm. The pulse duration is around 650 fs at a repetition rate ~100 MHz.