概述了高度各向异性的，尤其是无掺杂和掺杂的层状半导体GaSe和相关晶体InSe、GaS和GaSe-GaS(固溶液)的结构特性、光学特性和非线性光学特性的实验研究结果，同时概述了由共焦拉曼和光致发光显微镜研究得到的结果和由声波降解法和激光消融技术得到的GaSe纳米粒的光学性质。重点讨论了ε-GaSe的性质，指出其具有最大的光学二阶非线性系数χ，并可结晶成4种不同的多型体(ε,γ,β,δ)，且每个晶胞有以不同数目和排列方式的层状结构。研究认为，在红外和太赫兹光谱波段，GaSe可以被看作是最有应用前景的非线性晶体之一。已发表的1700多篇关于材料物理性质的论文也指出，在THz波段，GaSe是一种具有特异非线性光学特性的材料。通过共焦拉曼显微镜的实验研究，讨论了晶体的域结构和非线性光学性质。除了探讨这些材料最重要的物理性质，还进一步研究了在主边缘附近的光吸收，在红外和太赫兹波段的光致发光、非线性光学性质以及它们的纳米物理性质，这些研究对理解二维晶体结构和其物理性质之间的联系是必要的。由于GaSe及GaSe型晶体具有包含–Se-Ga-Ga-Se-共价键的单一四层结构，因而它们的纳米粒表现出一些特殊的性质。一些GaSe型晶体(InSe, GaTe)的带隙宽度在1.2~1.5 eV之间，这使得它们及其纳米粒很适合用作光伏材料。

The experimental and studied results of the structural, optical and nonlinear optical properties on the highly anisotropic especially un-doped and doped layered semiconductor GaSe (gallium selenide) and related crystals, InSe, GaS and GaSe-GaS (solid solutions) are overviewed. It includes also the investigation results on optical properties performed by confocal Raman and photoluminescence (PL) microscopy. Some experimental results on optical properties of GaSe nanoparticles obtained via ultrasonication and laser ablation methods are considered also.The properties of ε-GaSe is emphasized, which has one of the highest coefficient χ(2) of optical second-order nonlinearity and are crystallized into four different polytypes (ε,γ,β,δ), containing different number and arrangement of layers per unit cell. It is shown that GaSe may be considered as one of the best crystals for nonlinear applications in the IR range. More than 1 700 papers describe the physical properties of the GaAs and indicate that it is an outstanding material for applications to the teraherz (THz) spectral range. The domain structure of the crystal in connection with the Nonlinea Optical(NLO) properties is discussed by confocal Raman microscopy experiments. In spite most important physical properties of these materials are mainly investigated, further studies of optical absorption near the fundamental edge, PL, NLO properties in the IR and THz ranges as well as physical properties of their nanoparticles are necessary to understand the connection between the 2-D crystal structure and the physical properties. It is known that the nanoparticles of GaSe and GaSe- type crystals are highly interesting because they have a single tetra layer structure consisting of covalently bond –Se-Ga-Ga-Se- tetra layers. Some of GaSe-type crystals have band gaps in the range of 1.2-1.5 eV (InSe, GaTe) which make them and their nanoparticles suitable for photovoltaic applications.