Olivier Gauthier-Lafaye

Simultaneous two-state lasing in quantum-dot lasers

We demonstrate simultaneous lasing at two well-separated wavelengths in self-assembled InAs quantum-dot lasers, via ground-state (GS) and excited-state (ES) transitions. This effect is reproducible and strongly depends on the cavity length. By a master-equation model, we attribute it to incomplete clamping of the ES population at the GS threshold.

Experimental demonstration of nonreciprocal amplified spontaneous emission in a CoFe clad semiconductor optical amplifier for use as an integrated optical isolator

Experimental results are presented for an integrated-optical-waveguide-isolator concept. This concept is based on inducing the transverse magneto-optic Kerr effect in a semiconductor InP-based optical amplifier (SOA) by using a transversely magnetized ferromagnetic metal as an electrical contact. As a result, the SOA exhibits nonreciprocal loss/gain for TM polarized light and is easily monolithically integrated with other InP-based active photonic devices. We have designed, fabricated and characterized prototype ferromagnetic metal-clad optical amplifiers for an operation wavelength of 1300nm. In these first generation devices we obtained isolation strengths of up to 2.0dB∕mm.

Intersubband stimulated emission in GaAs/AlGaAs quantum wells: Pump-probe experiments using a two-color free-electron laser

Intersubband stimulated emission under optical pumping has been observed in the conduction band of GaAs–AlGaAs quantum wells. The asymmetric coupled quantum wells which exhibit three conduction bound levels are designed to exhibit population inversion under optical pumping. An optical excitation at λ=9.2 μm is used to bleach the absorption between the ground and second excited subband. The population inversion between excited subbands is pumped and probed on a picosecond time scale by a tunable two-color free-electron laser. The stimulated amplification is studied at low temperature in infrared waveguides as a function of the waveguide length and of the probe wavelength. A stimulated gain ≈80 cm−1 is measured at 12.5 μm in agreement with calculations.

First experimental demonstration of a monolithically integrated InP-based waveguide isolator

Abstract The architect should be equipped with knowledge of many branches of study and varied kinds of learning. This knowledge is mainly constructed by means of practice and theory (Vitrivius, 1914). Architectural education is considered to be a complex process. Its creative demands must be supported by an understanding of art, science, psychology, mathematics, engineering and etc. The design studio has long been the major component of architectural education. Traditionally it has involved a relatively small group of students under the direction of a studio master, and an instructor. This paper analyzes the characteristics of traditional studio environments, compares it with the constructivist studio in general and recommends a transformation in the design studio.

Long-wavelength (15.5-μm) quantum fountain intersubband laser InGaAs/AlGaAs quantum wells

A new type of semiconductor unipolar laser operating in the mid-infrared spectral region, the Quantum Fountain intersubband laser, is demonstrated. It is based on optical pumping of a three-bound-state coupled quantum well structure in the GaAs/AlGaAs material system. The lasing transition occurs between the two excited states. Population inversion can be achieved by benefitting from LO-phonon resonance between the two lower subbands. The optical pumping scheme enables a simpler design of the active region than electrically pumped intersubband lasers. Moreover, because doped layers and metallic contacts are not necessary for the operation of the Quantum Fountain laser, free-carrier and plasmon absorptions can be minimised, thus allowing long- wavelength operation. Large optical gains are measured using pump-probe experiments with a free-electron laser. Lasing action under optical pumping by a pulsed CO2 laser has been achieved at a record long wavelength of 15.5 micrometer with an output peak power of the order of 0.6 W at low temperatures.