Large field-induced refractive index change without red shift of absorption edge in five-step asymmetric coupled quantum wells with modified potential

1997 ◽  
Vol 9 (5) ◽  
pp. 639-641 ◽  
Author(s):  
H. Feng ◽  
J.P. Pang ◽  
K. Tada ◽  
Y. Nakano
Keyword(s):  
Refractive Index ◽  
Quantum Wells ◽  
Absorption Edge ◽  
Refractive Index Change ◽  
Red Shift ◽  
Large Field ◽  
Coupled Quantum Wells ◽  
Index Change

NONLINEAR OPTICAL PROPERTIES OF A HETERO-nipi STRUCTURE WITH COUPLED QUANTUM WELLS

2005 ◽  
Vol 14 (03) ◽  
pp. 449-460
Author(s):  
ALAN R. KOST ◽  
RON R. CARTER ◽  
ELSA M. GARMIRE ◽  
THOMAS C. HASENBERG
Keyword(s):  
Refractive Index ◽  
Quantum Wells ◽  
Absorption Edge ◽  
Nonlinear Optical ◽  
Refractive Index Change ◽  
Transition Strength ◽  
Electron Hole ◽  
Coupled Quantum Wells ◽  
Excitonic Absorption ◽  
Absorption Measurements

A light-induced broadening of excitonic absorption features was investigated for a hetero n-i-p-i structure containing coupled quantum wells. Light-induced differential absorption as large as 5000 cm-1 was observed with an irradiance of only 280 mW/cm2. The largest absorption change was positive and occurred at 814 nm, just below the absorption edge for the non-illuminated sample. The nonlinear optical response for this structure is unlike the response for conventional n-i-p-i structures which exhibit decreasing absorption below the absorption edge. A corresponding refractive index change was calculated from absorption measurements using a modified Kramers–Kronig relation. The maximum change in the refractive index was 0.01 at 818 nm, a wavelength where the absorption was small for both the illuminated and non-illuminated samples. The origin of the excitonic broadening is explained with calculations for the transition energy and transition strength of the four lowest energy optical transitions for the coupled quantum wells. The relatively low irradiance required to excite the sample is attributed to long electron-hole recombination time, measured to be between 100 and 700 μs, depending on the irradiance on the sample.

Nonlinear refractive index change and optical rectification in a GaN-based step quantum wells with strong built-in electric field

2015 ◽  
Vol 29 (05) ◽  
pp. 1550024 ◽  
Author(s):  
Li Zhang
Keyword(s):  
Refractive Index ◽  
Electric Field ◽  
Quantum Wells ◽  
Nonlinear Refractive Index ◽  
Structural Parameters ◽  
Refractive Index Change ◽  
Blue Shift ◽  
Optical Rectification ◽  
Airy Functions ◽  
Index Change

Based on the compact density matrix approach, the linear and nonlinear refractive index change (RIC) and optical rectification (OR) coefficients in a GaN -based step QW with strong built-in electric field (BEF) have been theoretically deduced and investigated in detail. The analytical electronic state is derived by the two airy functions. And the band nonparabolicity is taken into account by using an energy dependence effective mass (EDEM) method. Numerical calculations on a four-layer AlN / GaN / Al x Ga 1-x N / AlN step QW are performed, and the curves for the geometric factors, the linear, the nonlinear, the total RICs and the OR coefficients as functions of the structural parameters of the step QW are discussed. The features for these curves were specified and reasons for the features were explained reasonably. It is found that the decreasing of well width Lw, and step barrier width Lb and the doped concentration x in step barrier will result in the significant enhancement of the RICs. With the decrease of Lw, Lb and x, the resonant photon energies of RIC and OR coefficients have obvious blue-shift. Moreover, the RIC and OR coefficients behave different dependence on the structural parameters of the GaN -based step QWs. The profound physical reasons are also analyzed.

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