Waveguide‐Integrated Broadband Pyroelectric Photodetector on Thin‐Film Lithium Tantalate

Thin‐film lithium niobate (TFLN) and thin‐film lithium tantalate (TFLT) have emerged as promising material platforms for photonic integrated circuits recently. However, the wide bandgap intrinsically poses a challenge for on‐chip photodetection on these platforms, and heterogeneous integration of other semiconductor materials is always required, which is complex in fabrication and limited in working wavelength range. Here, we demonstrate the first waveguide‐integrated pyroelectric photodetector on x‐cut TFLT, which features a monolithic device structure and a broadband response. The proposed devices are theoretically studied and experimentally characterized from near‐infrared to mid‐infrared. For a 200‐µm‐long device, the measured peak voltage responsivity reaches 513 V/W under pulse modulated optical power and 206.6 V/W under sinusoidal modulated optical power. The measured noise equivalent power reaches 821.9 nW Hz −1/2 at 10 Hz, which is dominated by the read‐out circuit noise. Devices with similar configurations are also fabricated on x‐cut TFLN for comparison, which exhibit responsivities nearly an order of magnitude lower. Finally, a preliminary gas absorption spectrum measurement is conducted using the proposed detector, further confirming its potential for monolithic integration with other TFLT photonic devices for advanced applications such as power monitoring and broadband spectral sensing.