High power continuous-wave (CW) single frequency 780 nm lasers with excellent beam quality have received significant attentions for the growing important role in atomic physics and quantum optics. Narrow linewidth, frequency stable 780 nm laser can be provided by GaAs diode lasers with tapered amplifiers and Ti: sapphire laser. But diode lasers have poor output beam quality and Ti: sapphire based system is often costly, including its maintenance.

Recently, a research team led by Prof. FENG Yan from Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, reported a high power CW single frequency 780 nm laser by utilizing single-pass frequency doubling of a 1560 nm fiber amplifier in an MgO: PPLN crystal. The study was published in Optics Express.

In their experiment, the 780 nm laser with a maximum output power of 21.2 W was obtained under the incident 1560 nm power of 49.8 W, which gave the conversion efficiency of up to 42.6%. Researchers employed an in-band pumping scheme for the high power 1560 nm EDFA by a 1480 nm cascaded Raman fiber laser. The 1560 nm laser with maximum output power of 49.8 W was achieved at an incident 1480 nm laser of 60.6 W, corresponding to an efficiency of 79.7%. To date, this is the highest reported CW single frequency 780 nm laser system.

Their work demonstrated that efficient external-cavity single-pass frequency doubling of 1560 nm Erbium-doped fiber amplifier (EDFA) via PPLN crystals can be another way to generate 780 nm laser, which is simple, compact, and robust laser system for advanced quantum technology.

Such high power 780nm laser is urgently pursued for advanced quantum technology applications like large scale atom interferometers. Based on the 1480 nm in band core-pumping technique, further power scaling of the single frequency 1560nm erbium amplifier is foreseeable.

This work was supported by the National Key Research and Development Program of China, Science and Technology Commission of Shanghai Municipality.

Fig. 1 Schematic diagram of the high power 780 nm laser system. (Image by SIOM)
 
Fig. 2 The output power (a) and conversion efficiency (b) of the 780nm versus 1560nm power. (Image by SIOM)

Article website:
https://www.osapublishing.org/oe/abstract.cfm?uri=oe-27-24-35362

Contact:
Mr. CAO Yong
General Administrative Office
Shanghai Institute of Optics and Fine Mechanics, CAS
Email: caoyong@siom.ac.cn