OPO

Optical parametric oscillator

For creating squeezed light source in telecommunication band we may consider the following works by Roman Shnabel's and Pink Koy Lam's groups.

Work	Wavelength	Pump power	Squeezing achieved	Crystal	Type of cavity
Optics letters 43.1 (2018): 110-113	1550 nm	12 mW @ 775 nm	13 dB	9.3 mm PPKTP	Double resonant single sided half-monolithic standing wave cavity with reflectivity of 97.5% @ 775 nm and 85% @ 1550 nm.
Optics express 19.25 (2011): 25763-25772	1550 nm	180 mW @ 775 nm	12.3 dB @ 180 mW pump	9.3 mm x 2 mm x 1 mm PPKTP	Single resonant single sided half-monolithic standing wave cavity with reflectivity of 20% @ 775 nm and 90% @ 1550 nm.
Optics Express 30.21 (2022): 37213-37223	1550 nm	518 mW @ 775 nm	12.6 dB @ 518 mW of power	15 mm long PPKTP	Double resonant bow-tie traveling wave resonator with output coupler of 75% @ 1550 nm and finesse of 21 and cavity linewidth of 30 MHz. Mirrors have reflectivity of 99.9975 @ 1550 nm and 98 @ 775 nm.

Crystal parameters

For achieving degenerate parametric down conversion it is important to get phase matching for signal and idler at the same wavelength of interest. Considering achieving squeezing @ 1560.48 nm we may choose the proper parameters for the crystal. The parameters for the crystal can be estimated using calculator in spdccalc.org. For example, the parameters for Type 0 KTP phase matching.

Phase Matching type	Wavelength	Period polling
Type 0: e->e+e	Joint Phase wavelength 1560.48 nm	32.34 um
Type 0: o->o+o	Joint Phase wavelength 1560.48 nm	24.99 um
Type 1: e->o+o	Joint Phase wavelength 1560.48 nm	13.51 um