Electro-optic polarisation conversion at 0.8 K in titanium in-diffused lithium niobate waveguides

Abstract

We demonstrate an electro-optic polarisation converter for 1550nm at cryo genic temperatures in titanium in-diffused lithium niobate waveguides. The switching voltage increases, the modulation depth remains unchanged, and we show operation up to 25 MHz.

Cryogenic electro-optic modulation in titanium in-diffused lithium niobate waveguides

“…[33,17] to read out a superconducting device. Polarisation conversion under cryogenic conditions was recently demonstrated by our group [32]. Building on these initial results, in this paper we investigate the performance metrics of three classes of electro-optic modulators in lithium niobate under cryogenic conditions.…”

“…To integrate modulators with SNSPDs, the modulators must not only function at cryogenic temperatures, but also be compatible with the cooling power of the cryostat. Acousto-optics [37], thermo-optics [38,39], carrier injection [40], DC-Kerr [41] and the electro-optic effect [29,30,42,32,43] have been shown at cryogenic temperatures. Out of these effects, the electro-optic effect has great advantages for cryogenic applications since it only requires the generation of an electric field with electrodes and is preserved at cryogenic temperatures [29,30,31,32].…”

“…Acousto-optics [37], thermo-optics [38,39], carrier injection [40], DC-Kerr [41] and the electro-optic effect [29,30,42,32,43] have been shown at cryogenic temperatures. Out of these effects, the electro-optic effect has great advantages for cryogenic applications since it only requires the generation of an electric field with electrodes and is preserved at cryogenic temperatures [29,30,31,32]. We need to know how the electro-optic effect changes with a change in the temperature to integrate modulators with other optical components at cryogenic temperatures.…”

“…The mismatch in propagation speed results in an acquired phase difference ∆β. A periodic poling of the crystal axis along the propagation direction can compensate the accumulated phase difference [35,32]. Therefore, a poling length Λ should be chosen such that…”

“…Furthermore, superconducting single photon detectors such as transition edge sensors [22] and SNSPDs have been integrated in lithium niobate [23,24,25,26,27,28,17]. Finally, lithium niobate offers a large electro-optic effect for optical modulation, which is also functional at cryogenic temperatures [29,30,31,32,33]. [29,30], independently demonstrated a directional coupler in lithium niobate at low temperature for the first time.…”