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Unipolar Semiconductor Lasers


The primary objective of this project is to develop a new class of unipolar mid ir (3.5 to 15 m) semiconductor lasers (Quantum Cascade Lasers) for sensing applications, operating in pulsed mode at room temperature. These devices are based on intersubband transitions (ISBT) and as such their emission wavelength does not depend upon the gap of the constituent materials but is essentially determined by quantum confinement. Therefore, conventional III-V material can be used to design and fabricate mid ir lasers that would be ordinarily based on narrow-gap semiconductors. In addition these lasers will be provided with shallow gratings for wavelength selection (DFB technology) and finally mounted on Peltier elements for temperature stabilisation and wavelength tuning. The final result of the project will consist of a prototype sensing system characterised by high sensitivity, compactness, low cost and maintenance which will be easily accepted to different installations following specific industrial requirements. The core of this project is not an incremental work on existing technology but is the opening and development of a new semiconductor device technology to aid the European industries and know-how to expand against the US hegemony in this field. It is in this pioneering spirit that this proposal is submitted for approval to BRITE-EURAM BASIC RESEARCH. Laser spectroscopy is the ultimate tool to accurately measure narrow absorption lines in the mid-ir spectral region (3 - 15 1lm).

Today the only commercially available sources suitable for such applications are semiconductor lead salt lasers, which operate only at cryogenic temperature. All other sources are either too bulky and costly (OPO and FEL) or limited to fixed wavelengths (gas lasers). Marketing research has identified a strong industrial and environmental need for gas monitoring and sensing if the total cost of the system drops to 10-20 kECU (less than half of the present value). The industrial sectors where unipolar semiconductor lasers should have strong impact include: sensors for detection of trace gas-waste at the point of discharge into the environment, industrial monitoring for production-line quality control (e.g. H.O monitoring in pyrotechnic, pharmaceutical and food industries), in-situ control of combustion processes. The consortium brings together the competency necessary to the realisation of such a complex device where solid state physics and optics merge with quantum mechanics. The partnership includes two growth facilities (THCSF focused on the growth of strained GaInAs/AIGaAs/GaAs; FKE for the growth of lattice matched GaAs/AIGaAs) and three processing facilities (THCSF, FKE, UNN) where the device will be fabricated.

UNN will address technological issues such as the development of DFB lasers at selected wavelengths. At UPS the optical pumping scheme will be investigated; INFM will support partners with device modelling and band structure calculation for all material systems and will carry out spatial and spectral characterisation of output beams. Finally Muted and Orbisphere (end users) will incorporate lasers into newly designed commercial systems. This effort target the investigation and full exploitation of full exploitation of the wide range of emission wavelengths offered by unipolar lasers based on technologically mature III-V materials BE97-4072.



Participants (6)

Istituto Nazionale per la Fisica della Materia
Piazza Dei Cavalieri 7
56127 Pisa
Arzbergerstraße 10
82211 Herrsching
Orbisphere Laboratoires SA
20,Rue Du Puits-godet
2000 Neuchatel
Technische Universität Wien
1040 Wien
1,A.-l. Breguet 1
2000 Neuchatel
Université Paris Xi - Bètiment 414
91405 Orsay