III-V nanophotonic devices

Photonic crystal lasers :

The benefits offered by Photonic Crystal to improve performances and functionalities of semiconductor laser is an active field of research within the Photonic group. This fields covers several architectures ranging from all-Photonic Crystal lasers to hybrid lasers mixing Photonic Crystal with more conventional laser fabrication techniques.

 

 
SEM image of an array of single-mode, Photonic-Crystal DFB lasers on suspended (In)GaAs membranes; Inset: close-up on the W3 GK defect photonic crystal waveguide defining the laser cavity.
 
  

Distributed FeedBack (DFB) lasers based on defect photonic waveguide have been investigated by the team over the last decade.
This effort was carried out and supported by several projects (CRISTEL, ..., MIDAS) with a particular focus on single mode emission and wavelength control in laser cavity entirely defined by photonic crystals.
In particular, arrays of precisely detuned, single-mode DFB lasers that are immune to optical feedback were demonstrated on GaAs membranes emitting at 990nm.
Within the MIDAS project (in collaboration with Montpellier University), we aim to extend these studies to GaSb bulk photonic crystal DFB laser arrays emitting around 2.3 and 2.6 microns for gas sensing. The core idea of the MIDAS project is to multiplex several single-mode and slightly tunable DFB lasers emitting at precisely set wavelengths to improve Tunable Diode Laser Absorption Spectroscopy by using a source with no moving parts.

Related publications:

 

 
Experimental characterization of Photonic Crystal membrane random laser under optical pumping: in addition to diffusive emission at 800 nm, two speckle-like laser modes are emitted around 803 and 805 nm.
 
  

Lasing action in optically pumped random lasers in the low diffusive regime.
Within the project GLAD (in collaboration with Nice University) we studied laser emission in a planar active random structure constituted by a random photonic crystal on an active GaAs membrane. The key idea of this project was to harness the fabrication technique developped for Photonic Crystal membrane laser to build planar and active diffusive medium offering easy optical access to the lasing mode through the membrane's surface. During this project, we developped specific technological steps to fabricate large area (up to 100x100µm²) random photonic crystal membrane together with a dedicated microphotoluminescence hyperspectral imager for the experimental characterization of the fabricated random lasers.

Related publications:

 

 
Detailed view of the Photonic Crystal reflector that couples the two sections of the tunable ridge laser emitting in the MIR.
 
  

PhC coupled cavity lasers in the MIR for CH4 detection.
Within the CRISPI project (in collaboration with Montpellier university), we investigated edge-emitting lasers which combined conventional fabrication methods to define electrically-pumped ridge sections and e-beam lithography and sub-micron-scale dry etching to introduce photonic-crystal cavity couplers.
This mix and match fabrication approach allowed us to achieve record high sensitivity of QPAS (Quartz Laser Photo-Acoustic Sensing) with these lasers.

Related publications:

High contrast grating VCSELs:


 
Mid-infrared electrically-pumped VCSEL including AlOx lateral confinement and GaAs/AlOx High-Contrast Grating mirror.
 
  

The sub-wavelength diffraction regime is a unique tool to tailor laser beam properties. In the case of VCSEL (Vertical Cavity Surface Emitting Laser), the output Bragg reflector can be advantageously replaced by a high contrast grating mirror, thus opening the path to numerous optical integrated functionalities. This evolution of the geometry and the impact on the performances has already been demonstrated by different groups on 850 and 1550-nm VCSELs.
The goal of the ANR MARSUPILAMI project is to transfer this concept to VCSEL in the mid-infrared range and thus improving their efficiency and expanding their capabilities (polarization single-mode output beam). Our collaborative partnership (LAAS-CNRS, IES Univ. Montpellier 2 and LMOPS Supelec-Metz) is structured in several parts:

  • the lateral wet thermal oxidation of AlAs layers and AlAsSb to achieve the electrical and optical confinements in the cavity of the VCSEL.
  • The design of a mirror with GaAs/AlOx sub-wavelength grating, allowing optimal properties for use in laser structures while benefiting of a wide tolerance for the manufacturing processes.
  • The development and control of manufacturing processes, ranging from the VCSEL epitaxial multilayer structures by combining antimonide and arsenide materials, through the production of sub-micronic structures with optical technology of nanoelectronics and dry etching processes, up to the manufacturing of the VCSEL device.

As a conclusion, the synthesis of all these computing and numerical methods, the technological and characterizations studies have contributed to the integration of all these technological bricks in a VCSEL emitting around 2.3μm.

Related publications:

Integrated nonlinear optics and integrated optical comb generation:

 

 
Array of micro-disks resonators vertically coupled to access waveguides. Both resonators and waveguides are defined by AlOx diaphragm.
 
  

Frequency combs are novel optical sources which emit a set of equi-spaced frequencies whose prime potential applications include metrology, telecommunication synchronization, high-purity RF synthesizers, astronomical calibration, advanced spectroscopy.
Our work aims to evaluate the feasibility of realizing an optical frequency comb using an all semiconductor technology. The considered approach is unusual in that it aims to use intra-cavity Kerr-effects in a micro-ring configuration to generate this frequency comb rather than the saturable-absorber-induced mode-locked operation as exploited in more conventional devices and may thereby overcome the dispersion and gain bandwidth limitations associated with the latter devices. The activity covers all aspects of the work i.e. design, fabrication using GaAs/AlOx technology as well as device characterisation.

Related publications: