Fig. 2: All-optical poling and second-harmonic generation.
From: Ultrabroadband milliwatt-level resonant frequency doubling on a chip
A Micrograph of a typical device in frequency doubling operation. The visible camera (left) emphasizes the resonant field enhancement of the generated SH in the north loop, while the infrared (IR) camera (right) shows the field enhancement in the south loop. Note that the two fields overlap in the shared path, where AOP and simultaneous SHG occur. B Typical experimental SHG spectrum, showing generated light at 770 nm (pump attenuation: 27.5 dB). C Collection of SHG spectra associated with pumping in the C and L bands (resolution: 1 nm). Each trace is a detail of a spectrum as shown in panel (B). The heater currents are slightly adjusted for each data point to optimize the generated power. D Two-photon and (E) one-photon micrograph of one of the devices after inscription of the nonlinear QPM grating through AOP. TPM imaging reveals a periodic ∣χ(2)∣2 distribution that only exists in the interaction region, confirming the linearly uncoupled nature of the process.
