Effect of Si δ-Doping on the Linear and Nonlinear Optical Absorptions and Refractive Index Changes in InAlN/GaN Single Quantum Wells

In the framework of effective mass approximation, we theoretically investigate the electronic structure of the Si δ-doped InAIN/GaN single quantum well by solving numerically the coupled equations Schrodinger-Poisson self-consistently. The linear, nonlinear optical absorption coefficients and relative refractive index changes are calculated as functions of the doping concentration and its thickness. The obtained results show that the position and the amplitude of the linear and total optical absorption coefficients and the refractive index changes can be modified by varying the doping concentration and its thickness. In addition, it is found that the maximum of the optical absorption can be red-shifted or blue-shifted by varying the doping concentration. The obtained results are important for the design of various electronic components such as high-power FETs and infrared photonic devices.

Refractive Index Change and Color Center Formation in LiYF_4 Crystal Induced by a Femtosecond Laser

The refractive index change and color centers formation in LiYF4 crystal at room temperature are induced by a femtosecond laser irradiation. A mechanism for refractive index change and color centers formation is proposed.

A novel coupled quantum well structure with large field-induced refractive index change and low absorption loss at 1.55 μm

A novel coupled quantum well structure - quasi-symmetric coupled quantum well （QSCQW） is proposed. In the case of low applied electric field （F = 25 kV/cm） and low absorption loss （a ≈ 100 cm^-1）, a large field-induced refractive index change （for TE mode, △n = 0.0106; for TM mode, △n = 0.0115） is obtained in QSCQW structure at operating wavelength λ = 1550 nm. The value is larger by over one to two order of magnitude compared to that in a rectangular quantum well （RQW） and about 50% larger than that of five-step asymmetric coupled quantum well （FACQW） structure under the above work conditions.

Optical absorption via intersubband transition of electrons in GaAs/Al_xGa_(1-x)As multi-quantum wells in an electric field

Based on the effective mass approximation, the Schrodinger equation and Poisson equation in GaAs/AlGaAs multi-quantum wells(MQWs) are self-consistently solved to obtain the wave functions and energy levels of electrons in the conduction band for the ground first excited state by considering a lateral electric field(LEF). Then, the effects of size, ternary mixed crystal, doping concentration, and temperature on linear and nonlinear intersubband optical absorption coefficients(IOACs), and refractive index changes(RICs) due to the transition between ground states and the first excited states of electrons are discussed based on Fermi’s golden rule. The results show that, under a fixed LEF, with increase of A1 composition and doping concentration, the IOACs produce a red shift. With increases of both widths of the wells and barriers IOACs appear as blue shifts and their amplitudes increase, but the barrier width change is much more important to affect nonlinear IOACs, whereas increasing the temperature results in a blue shift first and then a red shift of IOACs. When the other parameters are fixed but there is an increase in the LEF, IOACs occur with a blue shift, and the RICs have similar properties.