We describe a method for reducing the temperature sensitivity for spontaneous parametric down conversion (SPDC) suitable for generating entangled time-frequency quantum photonic states in the telecommunication band at a wavelength of 1550 nm. We present specific design examples using periodically-poled LiNbO3 waveguides, which are commercially available and have a high second-order nonlinear coefficient that improves the overall device efficiency. One method uses two distinct poling regions, each with a poling period selected for phase-matching at different temperatures. The temperature bandwidth is increased from ~5 °C to ~17 °C using this approach, while only reducing the overall efficiency of the process by a factor of 4. The bandwidth is large enough so that controlling the overall temperature of the nonlinear crystal is likely not needed in a laboratory environment or can be achieved using a low size, weight, and power temperature controller design for field-deployed sources. To improve the stability of the design, we propose using a differential heating method where only the difference in the temperature is stabilized. The differential temperature stabilization method requires a smaller, lighter weight heater and lower power than other approaches, thus greatly simplifying the overall design. Additionally, we show that the system is less sensitive to fluctuations in the pump laser’s wavelength for the two-region approach. Finally, we generalize the design to multiple poling regions.
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