O. Gauthier-Lafaye

Oxide confinement and high contrast grating mirrors for Mid-infrared VCSELs

A new mid-infrared (MIR) Vertical Cavity Surface Emitting Laser (VCSEL) structure is proposed. We have integrated to the VCSEL structure both an oxide aperture for lateral confinement, and a sub-wavelength high-contrast-grating top mirror. Upon the GaSb-based half-VCSEL, we have grown a metamorphic AlGaAs heterostructure to enable thermal oxidation and grating mirror fabrication steps. A methodology based on optimization and anti-optimization methods has been used to design the optical grating, with improved parameter tolerances regarding processing errors. Finally, we show the complete fabrication of an electrically-pumped MIR monolithic VCSEL structure implementing both oxide confinement and a subwavelength grating top mirror.

Robust and simplified cat's-eye external-cavity lasers using cavity resonant integrated grating filters

We present a simple frequency-selective 3-element cats-eye cavity laser enabled by a new optical element, the so-called Cavity Resonant Integrated Grating Filter (CRIGF). Output powers in excess of 30 mW are achieved with single-mode emission. Discrete tuning around a central wavelength of 850 nm is achieved over a 30 nm band using a semiconductor source with an AR coated output facet. We will discuss the performance of the laser source together with new requirements for the CRIGFs. The road to enhanced performance will be outlined.

Soft mold NanoImprint Lithography: a versatile tool for sub-wavelength grating applications

Due to its independency to the substrate used, Soft mold NanoImprint Lithography (S-NIL) is a technique of great interest nin particular for the fabrication of optical devices. We demonstrate a mature pathway for the fabrication of optical filters nfrom the conception to the optical characterization. Those filters can be fabricated on large surfaces (up to 600 diameter nwafers) with high conformity on various substrates. Quality of the transfer will be discussed throughout the process and noptical performances compared to those obtained with classical techniques. In this paper we fabricated tunable spectral nfilters with a grating periodicity down to 260 nm and imprint surfaces up to 600. Physical conformity of the gratings will be ndiscussed in terms of long-range stitching obtained on 600 Si hard mold, dimensional shrinkage during thermal NanoImprint non Zeonor(R) soft mold and conformity towards patterned hard mold throughout the process.

Soft mold NanoImprint Lithography: A versatile tool for sub-wavelength grating applications

Due to its independency to the substrate used, Soft mold NanoImprint Lithography (S-NIL) is a technique of great interest in particular for the fabrication of optical devices. We demonstrate a mature pathway for the fabrication of optical filters from the conception to the optical characterization. Those filters can be fabricated on large surfaces (up to 6″ diameter wafers) with high conformity on various substrates. Quality of the transfer will be discussed throughout the process and optical performances compared to those obtained with classical techniques. In this paper we fabricated tunable spectral filters with a grating periodicity down to 260xa0nm and imprint surfaces up to 6″. Physical conformity of the gratings will be discussed in terms of long-range stitching obtained on 6″ Si hard mold, dimensional shrinkage during thermal NanoImprint on Zeonor® soft mold and conformity towards patterned hard mold throughout the process.

1D crossed gratings for narrow band polarization insensitive reflective filtering

We present experimental characterizations of 1D crossed Guided Mode Resonant Filters (GMRFs) in the near infrared fabricated by nanoimprint lithography. We will show that subwavelength gratings up to 4″ diameter can be fabricated using such techniques. We compare the performances of the GMRFs to the performances of Fabry-Perot filters and discuss the sensitivity to fabrication inhomogeneity of these components.

Mid-infrared (∼4.65μm) cavity resonator integrated grating filters

Cavity Resonator Grating Filters are a novel generation of reflective filters [1], They exhibit tailorable and narrow spectral bandwdidth [2], high reflectivity and large angular acceptance [3]. Their properties make them particularly interesting as output couplers for compact, robust, simplified cats eye external cavity laser diodes. Indeed, laser diode stabilisation with such filters at 850 nm has already been demonstrated [4], Using graded CRIGF filters, tunable external cavity laser diodes have also been demonstrated [5]. Such filters working in the mid-infrared range could be extremely useful to build spectrally stabilized external cavity Quantum Cascade Laser diodes (QCLs) or even tunable external cavity QCLs.

Tunable graded cavity resonator integrated grating filters

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).

Full optical confinement in 1D mesoscopic photonic crystal-based microcavities: an experimental demonstration

Full light confinement in mesoscopic photonic crystal membranes, forming a mesoscopic self-collimating 1D Fabry-Perot cavity, was predicted by Magno et al. [Opt. Lett. 39(14), 4223-4226 (2014)], using 2D calculations. Mesoscopic self-collimating cavities enable full light confinement despite the lack of index- or bandgap-guiding along one direction due to the flatness of the cavity reflectors. In this paper, we study these cavities using 3D-FDTD modelling and demonstrate that 3D light confinement survives the high losses inherent to the out-of-plane diffraction. Furthermore, we report an experimental demonstration at telecom wavelength on GaAs membranes with Q factors above 1700. This structure may pave the way for the fabrication of innovative configurations devoted to biochemical sensing and optical tweezing for nanoparticle manipulation thanks to its translational invariance property.

All photonic crystal electrically pumped GaSb laser diodes emitting at 2.4 µm for gas sensing applications

We report on the design, fabrication and characterization of all-photonic-crystal, electrically-pumped, second-order DFB lasers arrays emitting around 2.4 μm. Lasers were fabricated using GaSb-based materials and optimized 2D photonic crystal waveguides geometry. Threshold in the range of 100-150 mA depending on the PhC period are measured. CW emission with high SMSRs of 35 dB are achieved. Such laser arrays with spectrally narrow, evenly spaced spectral lines, each line being slightly tunable with current and temperature, are of high interest for gas sensing with gas discrimination potential.

Full optical confinement in 1D Mesoscopic Photonic Crystal-based microcavities: A preliminary experimental demonstration

In this contribution we present the preliminary results of the experimental characterisation of Mesoscopic Photonic Crystal membrane-based microcavities. Thanks to the Mesoscopic Self-Collimation phenomenon, it is possible to achieve a full light confinement for non-paraxial excitation even in all positive-index, right-handed linear material based 1D Fabry-Pérot-like cavities having straight mirrors. The translational invariance offered by this geometry and the high Q factor make these cavities captivating for biochemical sensing, optical tweezing and nanoparticle manipulation.