An apparatus for optical detection of ultrasound includes one or more optical resonators (OR—；200), one or more optical passive-demodulation interferometers (OPDI—；22), and one or more respective electro-optical readout circuits (EORC—；24). The one or more optical resonators (OR) are configured to modulate respective carrier frequencies of optical signals indicative of US waves impinging thereon. The one or more OPDI are implemented in one or more photonic integrated circuits (PIC), wherein each OPDI is configured to demodulate the optical signal output by the respective OR, so as to generate a respective intensity-modulated optical signal. Each OPDI includes an interferometer (32) having imbalanced arms (323, 325) that are recombined using an optical hybrid (34). The one or more respective EORC are each configured to measure the intensity demodulated optical signal produced by the respective OPDI, and to output a respective electrical signal.
