Dje. Knight et al., FREQUENCY-DOUBLING OF A FIBER-AMPLIFIED 1083 NM DBR LASER, The European Physical Journal. D: Atomic, molecular and optical physics, 3(3), 1998, pp. 211-216
A good frequency standard is required at 1083 nm for measurements on t
he fine structure of helium and of the fine structure constant. Severa
l milliwatts of CW frequency-doubled light offers the prospect of stab
ilisation to a Doppler-free hyperfine transition in molecular iodine.
The 1083 nm emission of an extended-cavity DBR diode laser has been am
plified using an ytterbium-doped fibre amplifier, and applied to a typ
e-I phase matched Mg:LiNTbO3 crystal in a high-Q fundamental-resonant
cavity for frequency doubling. The amplifier gain at 1083 nm under typ
ical operating conditions was 13.8 dB, with a coherent output power up
to 63 mW, limited by the maximum signal input power. The doubling cav
ity Q was similar to 2 x 10(7), and about 70% of the incident power wa
s coupled in. The maximum 2nd-harmonic conversion efficiency exceeded
20% and provided an output power of 3.7 mW for making continous freque
ncy scans of up to 600 MHz in the green. All optical spectrum analyser
at 541.5 nm showed fringes of 4.6 MHz full width half maximum, close
to the instrumental width.