Excitons at High Density in CdS and GaSe, and Optical Bistability

Abstract

Changes in the absorption and refractive index caused by laser absorption in CdS and GaSe are investigated and used to produce absorptive resonatorless bistability in CdS and to explain dispersive optical bistability in a GaSe Fabry-Perot cavity.Durch Laserabsorption hervorgerufene hderungen von Absorptions-und Brechungsindex wurden in CdS und GaSe untersucht. Mit ihrer Hilfe wird resonatorlose Bistabilitiit in CdS erreicht und dispersive optische Bistabilitiit in einem Fabry-Perot-Resonator in GaSe erklart.

Strong optical nonlinearities in gallium and indium selenides related to inter-valence-band transitions induced by light pulses

“…As the absorption coefficient of the transition from valence band C to the conduction band decreases due to the conduction-band filling, the subsequent loss of oscillator strength is compensated by the appearance of a new transition from valence band C to the empty states of valence band B. According to studies of optical nonlinearities in the fundamental absorption edge of GaSe, [11][12][13] exciton screening and band-filling effects are observed at excitation rates ranging from 10 24 to 2 ϫ10 25 photons/cm 2 s, that are of the same order as those used in the experiments reported in Sec. III.…”

“…Gallium selenide ͑GaSe͒ is a III-VI layered semiconductor that has been widely investigated during the last few years due to its outstanding nonlinear optical properties. Results on harmonic generation, [1][2][3][4][5][6] parametric oscillation, 7 or frequency mixing [8][9][10] in the near and middle infrared, as well as effects related to excitonic optical nonlinearities giving rise to optical bistability, [11][12][13][14][15] can be found in the literature. Indium selenide ͑InSe͒, belonging to the same family, has also been investigated as a frequency doubler in the middle infrared.…”

Band structure of indium selenide investigated by intrinsic photoluminescence under high pressure

“…14,15 In particular, gain and stimulated emission measurements in these materials have been performed by different authors and several hypotheses have been argued to explain the nature of the stimulated emissions at room and low temperatures. [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] Many of these studies (performed during the latest 40 years) failed in correlating the unusual electronic properties of these compounds and the electronic band structure obtained from theoretical calculations. The main reason for the failure was the lack of detailed knowledge of the electronic band structure near the fundamental band gap.…”

Transport properties of nitrogen doped p-gallium selenide single crystals

“…Gallium selenide ͑GaSe͒ has been widely investigated in the last years because of its outstanding nonlinear optical properties. [1][2][3][4][5][6][7][8] The possibility of preparing GaSe high-quality thin films through the so-called van der Waals epitaxy [9][10][11][12] has lead to a renewed interest because of the potential optoelectronic applications. The problem of doping, that was early investigated without drawing definitive conclusions, [13][14][15][16][17][18] has been recently attacked by other groups that have specially studied the role of group II impurities as acceptors in GaSe.…”