Objective
Mid-infrared light (6 - 12 µm) generation is of prime importance for pollution detection. We propose to investigate a new avenue for realizing room temperature tuneable single mode 6-12 µm optical source of sufficient power for future real world applications. An optical parametric oscillator will be realized using a monolithic semiconductor cavity with two highly reflecting optimised Bragg mirrors grown on both side of a <111> GaAs wafer. The originality of this project are the following:
i) the wafer thickness will be chosen near the parametric interaction coherence length which is large in the infrared (2 - 10 µm) region so that large parametric gain will be obtained per pass;
ii) Bragg mirror structure will be a trade off between optimisation of the relative phase of interacting waves and minimum growth duration. This project will open the way towards extremely compact tuneable coherent sources pumped by micro-chip lasers. Mid-infrared light (6 - 12 µm) generation is of prime importance for pollution detection. We propose to investigate a new avenue for realizing room temperature tuneable single mode 6-12 µm optical source of sufficient power for future real world applications. An optical parametric oscillator will be realized using a monolithic semiconductor cavity with two highly reflecting optimised Bragg mirrors grown on both side of a <111> GaAs wafer. The originality of this project are the following:
i) the wafer thickness will be chosen near the parametric interaction coherence length which is large in the infrared (2 - 10 µm) region so that large parametric gain will be obtained per pass;
ii) Bragg mirror structure will be a trade off between optimisation of the relative phase of interacting waves and minimum growth duration. This project will open the way towards extremely compact tuneable coherent sources pumped by micro-chip lasers.
OBJECTIVES
The objective of this project is to develop a mid infrared (mid-IR) coherent source tuneable between 6 and 10 µm for future use in pollution remote sensing. This source is based on a new concept of monolithic optical parametric oscillator (OPO) realized in a GaAs cavity with two Bragg mirrors epitaxially grown on each side of the <111> wafer. Since optical dispersion of GaAs is small in the mid-IR, large coherence lengths are displayed for 6 to 12 µm idler generation. The wafer thickness is thus optimised to be:
i) close to 3 or 5 coherence lengths for high yield and handiness of the wafers and;
ii) highly resonant on the signal frequency to decrease the oscillation threshold. If successful, this assessment phase would be the first demonstration of a GaAs based OPO and would lead the way to compact mid-IR largely tuneable sources pumped by micro-chip lasers.
DESCRIPTION OF WORK
The project consists in the realization of a monolithic optical parametric oscillator (OPO) based on a semi- conductor cavity. The thickness of the GaAs wafer is chosen close to the coherence length of the parametric interaction.
Since optical dispersion is small in the mid-infrared, this length is sufficiently high (>50 µm) so that:
i) the wafers are handy if a even number of coherence lengths is chosen (3 or 5) and;
ii) reasonable conversion yields are obtained in a single pass thanks to GaAs extremely high optical nonlinearity.
Bragg mirrors are epitaxially grown on top of each side of the wafer in order to yield high reflectivity for the signal wave (R=99.5%). Double resonance is not chosen because of the difficulty to obtain stationary phase conditions on both waves with a single Bragg mirror. Preleminary calculations show that oscillation threshold should be obtained for a reasonnable amount of pumping fluence.
The sample fabrication presents the double difficulty of:
i) growth on a <111> surface and;
ii) epitaxy on both side of a wafer.
Experiments of resonant difference frequency generation, which are far easier to obtain than parametric oscillations, will be performed on the sample in a intermediate step to validate the concepts (coherence length, conversion yield e.g.) using infrared waves generated by an available home made OPO. If successful, this project would be followed by a more thorough programme for the development of a microchip laser pumped OPO, generating single-mode tuneable coherent light in the mid-infrared (6 to 12 µm).
Fields of science (EuroSciVoc)
CORDIS classifies projects with EuroSciVoc, a multilingual taxonomy of fields of science, through a semi-automatic process based on NLP techniques. See: The European Science Vocabulary.
CORDIS classifies projects with EuroSciVoc, a multilingual taxonomy of fields of science, through a semi-automatic process based on NLP techniques. See: The European Science Vocabulary.
- engineering and technology environmental engineering remote sensing
- natural sciences earth and related environmental sciences environmental sciences pollution
- natural sciences physical sciences electromagnetism and electronics semiconductivity
- natural sciences physical sciences astronomy observational astronomy infrared astronomy
- natural sciences physical sciences optics laser physics
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Coordinator
92322 CHATILLON CEDEX
France
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