A reflective cavity is used to make the basic frequency laser light passing through a second harmonic generation ( SHG ) crystal many time to increase the efficiency of SHG out of the laser resonant cavity, Two arrangements of light path are described. 本文介绍在腔外倍频中，加反射腔，使经过倍频后剩余的基频光，被反射腔多次反射叠加在原基频光上，增加了基频光功率，从而提高了倍频效率。
With the increasingly tense energy consumption, low efficiency of traditional incandescent light is bound to be replaced by a new generation of lighting. LED lighting for its high luminous efficiency, reliable will replace the traditional way of lighting, and cause lighting revolution. 随着能源消耗的日益紧张，发光效率较低的传统白炽灯必然要被新的照明方式所取代，LED照明以其发光效率高，可靠稳定必然代替传统的照明方式，引起照明领域的革命。
High intensity-discharge lamp ( HID ), an energy-saving light source of a new generation, has been widely applied in transportation, civil infrastructure, and factories for its high efficiency and long life. 节能型的新一代电光源高强度气体放电灯（HID）已经广泛应用于交通、市政、工厂等照明中，其具有光效高，寿命长等优点。
LED ( Light Emitting Diode ) is a new generation of light resource, known as " green light ", which is characterized as high efficiency, energy-saving, environment-friend, long life and high reliability. LED is gradually replacing traditional lighting. LED（LightEmittingdiode）是新一代光源，也称作绿色光源，具有高效、节能、环保、寿命长、可靠性高等优点，正逐步取代传统照明，成为新一代照明光源。
Light emitted diode ( abbr. LED ) is regarded as the fourth generation of lighting source with the advantages of no-mercury, environment-friendly, high efficiency, long-life and energy saving characteristics. 发光二极管（简称LED）具有不含汞、环保、高效、长寿命、节能等优点，被认为是第四代照明光源。
