5. Applications
5-2. Light Source for Optical Pumping of Solid-State Laser
The laser diode (LD) can be used as a light source for optical pumping of solid-state laser. Since LD excited solid-state lasers offer many advantages as listed below, it began to attract wide attention in recent years. Intensive efforts are now being made for development and commercialization.
- Provides overall high power efficiency.
- Features small size and light weight characteristics, making it possible to reduce power supply.
- Enables to operate without water cooling.
- Offers longer life and higher reliability than the lamps, contributing to a substantial reduction in maintenance cost.
- Enables to be used for optical pumping of various types of solid-state lasers 770 to 840nm in absorption wavelength.
The following table shows a comparison of the LD with the conventional excitation techniques in efficiency, etc.
To explain the excitation technique dependent differences in efficiency, it is necessary to compare the light emission spectra of inert gases such as xenon and krypton and those of laser diode with respect to the absorption spectra of Nd: YAG.
Nd: YAG and Nd: Glass, as shown below in Fig (a) and Fig (a´), have sharp absorption bands including 810nm.
If they are excited by use of a xenon or krypton lamp shown below in Fig. (b) and Fig. (b´), poor excitation efficiency will result, because such inert gas lamps have a wide light emission wavelength range in which even the wavelengths that are not absorbed by Nd: YAG and Nd: Glass are included. The laser diode, on the other hand, has a sharp light emission spectrum and offers a high pumping efficiency, because it allows tuning of wavelengths to only the 810nm absorption band.
