## Abstract

We report the results of an experimental and theoretical study of electron–hole competition in $\mathrm{CdTe}:\mathrm{Ge}$ photorefractive crystal with an incoherent auxiliary illumination and alternating low-frequency field. Resonant two-wave mixing (TWM) gain enhancement is studied that has been found depending on the wavelength and intensity of the incoherent illumination. We show that a low-frequency ac field can be used for an effective TWM gain enhancement under conditions appropriate to the electron–hole resonance. A time oscillation of the photorefractive gain concerned with the ac field is studied experimentally, and self-generation of time subharmonics is reported.

© 2007 Optical Society of America

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### Equations (10)

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(1)
$${E}_{SC}=im\frac{{G}_{Rn}-{G}_{Rp}}{{G}_{n}(\frac{1}{{E}_{q}}+\frac{1}{{E}_{Dn}-i{E}_{0}})+{G}_{p}(\frac{1}{{E}_{q}}+\frac{1}{{E}_{Dp}+i{E}_{0}})},$$
(2)
$${E}_{q}=\frac{e}{\epsilon K}\frac{{N}_{n}{N}_{p}}{{N}_{n}+{N}_{p}},\phantom{\rule{1em}{0ex}}{E}_{Dn}={E}_{Mn}+{E}_{D},\phantom{\rule{1em}{0ex}}{E}_{Dp}={E}_{Mp}+{E}_{D},$$
(3)
$${E}_{D}=K\frac{{k}_{B}T}{e},\phantom{\rule{1em}{0ex}}{E}_{Mn}=\frac{{\gamma}_{n}{N}_{p}}{{\mu}_{n}K},\phantom{\rule{1em}{0ex}}{E}_{Mp}=\frac{{\gamma}_{p}{N}_{n}}{{\mu}_{p}K}.$$
(4)
$${\alpha}_{n}\left(\lambda \right)={\alpha}_{n0}\phantom{\rule{0.2em}{0ex}}\mathrm{exp}[-{(\lambda -{\lambda}_{n})}^{2}\u2215\mathrm{\Delta}{\lambda}_{n}^{2}],$$
(5)
$${\alpha}_{p}\left(\lambda \right)={\alpha}_{p0}\phantom{\rule{0.2em}{0ex}}\mathrm{exp}[-{(\lambda -{\lambda}_{p})}^{2}\u2215\mathrm{\Delta}{\lambda}_{p}^{2}],$$
(6)
$${G}_{n,p}=\frac{1}{2\pi \hslash c}[{\alpha}_{n,p}\left({\lambda}_{A}\right){\lambda}_{A}{I}_{A}+{\alpha}_{n,p}\left({\lambda}_{R}\right){\lambda}_{R}{I}_{R0}],$$
(7)
$$g=\frac{1+\beta}{1+\beta \phantom{\rule{0.2em}{0ex}}\mathrm{exp}(-\Gamma L)},$$
(8)
$$\Gamma =\frac{4\pi {n}^{3}{r}_{41}\phantom{\rule{0.2em}{0ex}}\mathrm{Im}\left({E}_{SC}\right)}{\sqrt{3}{\lambda}_{R}m},$$
(9)
$$R=\frac{{I}_{A}}{{I}_{R}}=\frac{{\alpha}_{n}\left({\lambda}_{R}\right)-{\alpha}_{p}\left({\lambda}_{R}\right)}{{\alpha}_{p}\left({\lambda}_{A}\right)-{\alpha}_{n}\left({\lambda}_{A}\right)}\frac{{\lambda}_{A}}{{\lambda}_{R}}.$$
(10)
$$g={g}_{0}[1+\sum _{k=1}^{8}{c}_{k\u22152}\phantom{\rule{0.2em}{0ex}}\mathrm{sin}(\frac{2\pi k{f}_{0}t}{2}+{\phi}_{k\u22152})],$$