A wavelength tunable 2-ps pulse VECSEL

Abstract

We report a mode-locked Vertical-External-Cavity Surface-Emitting Laser (VECSEL) that exhibits 13.7 nm of tuning around a centre wavelength of 1042 nm. The wavelength tuning is achieved by incorporating an uncoated, 25 µm thick, fused silica etalon into the cavity of the laser at Brewster's angle. The etalon is then tilted with respect to the cavity axis. The etalon has a calculated free spectral range of 14 nm at normal incidence. The repetition rate of the laser is measured to be 1.88 GHz. The pulse duration, averaged over the tuning range, is 1.9 ps corresponding to a mean time bandwidth product of 0.46. For a sech 2 pulse this is 1.46 times larger than the transform limit. The average power of the laser does not fall below 2.6 mW and, over the tuning range, averages 3.5 mW. With appropriate amplification, such a laser would be highly suited to the generation of heralded single photons in photonic crystal fibre.

Dual-wavelength fiber-laser-based transmission of millimeter waves for 5G-supported Radio-over-Fiber (RoF) links

“…Further, two polarization controllers (PCs) are incorporated in the lasercavity with an optical isolator (ISO), forming a nonlinear polarization rotation configuration to control the birefringence for achieving an optimum amplification at the stable lasingaction [32]. Instead of using fused silica etalon as a tunable filter [33], a high-birefringence fiber (HiBi) has been used in this work as a birefringent filter and also to mitigate the inhomogeneous broadening of the Er-doped gain fiber. The HiBi fiber is also incorporated with two PCs to provide a wavelength-dependent polarization rotation with an optimum amplification performance by attaining a linearly polarized output.…”

Study of dielectric coatings for broadband operation of surface-emitting semiconductor lasers

“…Etalons have been primarily used in ML-VECSELs, and they are preferable as they can be thinner than birefringent filters (BRFs). Therefore, they do not introduce high dispersion in the cavity [17,18]. It is challenging to design gain chips that simultaneously fulfill the requirements for high power and broad gain bandwidth, whether in ultrashort pulse or tunable narrowband operation.…”

Graphene saturable absorbers for VECSELs

“…50:1 11 ) and a high damage threshold (>0.21 J/cm 2 ) 11 . However, SESAMs, epitaxially grown on lattice-matched semiconductor substrates 10 , only offer a limited operation bandwidth (to date, the broadest tuning range of VECSELs mode-locked with SESAMs is 13.7 nm) 12 and have a recovery time ranging from several hundreds of fs 13 to tens of ps. 11 Graphene based saturable absorbers (GSAs) have emerged as a promising SAs for ultrafast pulse generation, since graphene offers broadband operation and ultrafast recombination dynamics in the order of tens of fs.…”