Single and Multi-Person Face Recognition Using the Enhanced Eigenfaces Method

This research studies and analyzes the possibility of single-person and multi-person face detection and recognition. Face detection is performed by the Viola-Jones face detection method and recognition is performed by the Eigenfaces method. Unchanged face detection and recognition methods are explained and tested to their limits. Improvement in face recognition is achieved by observing the flaws of the Eigenfaces method and their enhancement

Theoretical investigation of new MgS-ZnSe structures

International audienceheoretical studies of the excitonic properties for different designs of MgS-ZnSe structures are presented. Excitonic binding energies are calculated for single quantum wells. For MgS-ZnSe superlattices, the energy of electron-hole transitions are evaluated and compared with the experimental photoluminescence spectra

Coherence dynamics in microcavities and polariton lasers

We study theoretically the second-order coherence g(2)(0) of light emitted by polariton lasers, i.e., devices based on stimulated relaxation and condensation of exciton–polaritons in microcavities. We solve kinetic equations for the polaritons in different approximations and show that (i) the coherence introduced into the polariton condensate by an external source can be conserved by the system over a macroscopically long time, and (ii) if the total number of polaritons is fixed by the excitation conditions, the correlations between the populations of the ground and excited polariton states can also result in the spontaneous buildup of second-order coherence in the polariton condensate. Both results are obtained neglecting polariton–polariton interactions in the condensate

Optical properties of single and double (111)-grown (Ga, In)As-GaAs strained-layer quantum wells under strong photo-injection

We show that manybody-effects and bandgap renormalization can be easily produced in strained-layer quantum wells with internal built-in piezo-electric fields, under photo excitation. Our observation was made at low temperature by comparing the behaviour of Ga0.92ln0.08As-GaAs strained layer single and double quantum wells grown along the (001) and (111) directions when the densities of photo-injected carriers is tuned over several decades. Comparison between experimental data and the results of a Hartree calculation including the space charge effects reveals that manybody interactions are efficiently photo-induced in the (111)-grown samples. Moreover, in the case of double quantum wells, additional transitions appear in the photoluminescence spectra, due to the tunnelling of the two first excited heavy-hole levels for moderate densities

Exciton binding energies and photo-induced tunnelling of carriers in (Ga,In)As-GaAs heterostructures grown with built-in piezoelectric field

We compare the binding energy of interacting electron and hole pairs in double quantum wells with and without internal piezo-electric fields. We show that the exciton binding is less sensitive to the piezo electric field than the oscillator strength. This allows many body-effects and bandgap renormalization to be easily produced in strained-layer quantum wells with internal built-in piezo-electric fields, under photo excitation. Our observation was made at low temperature by comparing the behaviour of Ga0.92In0.08As-GaAs strained layer single and double quantum wells grown along the (001) and (111) directions when the densities of photo-injected carriers are tuned over several decades. Comparison between experimental data and the results of a Hartree calculation including the space charge effects reveals that manybody interactions are efficiently photo-induced in the (111)-grown samples. Moreover, tunnelling of the two first excited heavy-hole levels can be stimulated for moderate carrier densities making such structure promissive for realising self electrooptic effect device (SEED) modulators

Performance simulation of interband laser diodes grown on InAs substrate

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