We report on the fabrication of a nonlinear cladding waveguide in BiB 3 O 6 crystal by using femtosecond laser inscription. The waveguide (with a nearly circular cross section of 150 m diameter) shows good guiding properties in two transverse polarizations. The guided-wave secondharmonic generation (SHG) at 532 nm green light has been realized under CW and pulsed wave pump at 1064 nm, based on the Type I birefringent phase matching configuration. The conversion efficiencies for CW and pulsed green laser SHG are 0.083 and 25%, respectively.

Extreme miniaturization of infrared spectrometers is critical for their integration into next-generation consumer electronics, wearables and ultrasmall satellites. In the infrared, there is a necessary compromise between high spectral bandwidth and high spectral resolution when miniaturizing dispersive elements, narrow band-pass filters and reconstructive spectrometers. Fourier-transform spectrometers are known for their large bandwidth and high spectral resolution in the infrared; however, they have not been fully miniaturized. Waveguide-based Fourier-transform spectrometers offer a low device footprint, but rely on an external imaging sensor such as bulky and expensive InGaAs cameras. Here we demonstrate a proof-of-concept miniaturized Fourier-transform waveguide spectrometer that incorporates a subwavelength and complementary-metal–oxide–semiconductor-compatible colloidal quantum dot photodetector as a light sensor. The resulting spectrometer exhibits a large spectral bandwidth and moderate spectral resolution of 50 cm−1 at a total active spectrometer volume below 100 μm × 100 μm × 100 μm. This ultracompact spectrometer design allows the integration of optical/analytical measurement instruments into consumer electronics and space devices.

We report on the operation of passively Q-switched waveguide lasers at 1 μm wavelength based on a graphene∕WS 2 heterostructure as a saturable absorber (SA). The gain medium is a crystalline Nd:YVO 4 cladding waveguide produced by femtosecond laser writing. The nanosecond waveguide laser operation at 1064 nm has been realized with the maximum average output power of 275 mW and slope efficiency of 37%. In comparison with the systems based on single WS 2 or graphene SA, the lasing Q-switched by a graphene∕WS 2 heterostructure SA possesses advantages of a higher pulse energy and enhanced slope efficiency, indicating the promising applications of van der Waals heterostructures for ultrafast photonic devices.

Abstract:We propose the use of kinoform diffractive lenses to focus near infrared femtosecond pulses in sapphire crystals for supercontinuum generation. It is shown that a strongly peaked structure appears in the blue region of the supercontinuum spectra. The central wavelength of this peak can be easily controlled by simply changing the lens-crystal distance. Moreover, when compared with the supercontinuum generated with a refractive lens in analogous conditions, the spectral extension of the sogenerated continuum is larger. Our results were corroborated for sapphire plates with different thicknesses as well as in other transparent dielectrics such as fused silica. ©2011 Optical Society of America

We report on the fabrication of three-dimensional waveguide beam splitters in a dielectric Bi(4)Ge(3)O(12) (BGO) crystal by direct femtosecond laser writing. In the laser written tracks of BGO crystal, positive refractive index is induced, resulting in so-called Type I configuration waveguiding cores. The "multiscan" technique is utilized to shape cores with designed cross-sectional geometry in order to achieve guidance at mid-infrared wavelength of 4 μm. The fundamental mode guidance along both TE and TM polarizations has been obtained in the waveguide structures. With this feature, we implement beam splitters from 2D to 3D geometries, and realize 1 × 2, 1 × 3, and 1 × 4 power splitting at 4μm.