Tunable graded cavity resonator integrated grating filters

Abstract

We demonstrated Graded Cavity Resonator Integrated Grating Filters (G-CRIGFs) that are narrowband spectral reflectors, spectrally tunable over more than 40 nm around 850 nm using a spatial gradient. A simple analytical model is introduced and validated experimentally to determine spectral performance of G-CRIGFs from the spectral properties of a standard Cavity Resonator Integrated Grating Filter (CRIGF).

Quasi-total backward reflection with a CRIGF under oblique incidence

“…We think that this configuration can be interesting when compared to the CRIGF used in normal incidence, because in the R − T direction, there is no Fabry-Perot interferences due to the substrate thickness, which are parasitic signals for filtering applications (for instance, the oscillations on the fig. 2 of [17] are due to the interferences coming from the thick substrate).…”

Thermally-tunable cavity resonator-integrated guided-mode resonance filters

“…3). Should the targeted Q-factor exceed 16000 [8], an improvement in spatial inhomogeneity would be required. to 80°C, the resonance is shown to shift over a 2.31-nm span, a range ~2.4-time the filter bandwidth (see Fig.…”

“…The only viable solutions therefore consist in altering the CRIGF micro-cavity physiccal properties either via its geometry or its constitutive set of refractive indices. To that extent, CRIGFs with spatially-graded grating structures have been successfully demonstrated [8] and used to introduce broadband tuning of ECDLs [9]. Nevertheless, to gain in laser stability and packaged module compactness, it is desirable to devise, demonstrate and implement systems exploiting displacement-free tunable filters.…”

Extended cavity quantum cascade laser with cavity resonator integrated grating filter

“…Basically, the GC act as an input grating coupler into a cavity mode localized in the waveguide and delimited by the 2 DBRs, resulting in a sharp reflectance peak at the resonant wavelength which is fixed by the grating period Λ GC . These filters exhibit highly interesting properties, such as narrow-bandwidth reflectivity with high angular tolerance [4], gradient-based tunability [5] and have already been used to setup external cavities for near infrared laser diodes [6]. The paper is organized as follow.…”