An imaging guidewire can include one or more optical fibers communicating light along the guidewire. At or near its distal end, one or more blazed or other Fiber Bragg Gratings (FBGs) can direct light to a photoacoustic transducer material that provides ultrasonic imaging energy. Returned ultrasound can be sensed by an FBG sensor. A responsive signal can be optically communicated to the proximal end of the guidewire, and processed such as to develop a 2D or 3D image. In an example, the guidewire outer diameter can be small enough such that an intravascular catheter can be passed over the guidewire. To minimize the size of the guidewire, an ultrasound-to-acoustic transducer that is relatively insensitive to the polarization of the optical sensing signal can be used. The ultrasound-to-optical transducer can be manufactured so that it is relatively insensitive to the polarization of the optical sensing signal.

An opto-acoustic measurement device detects and images buried structures in a sample, such as voids or other underlying structures, using a fixed delay time between pulses in the pump beam and pulses in the probe beam, while continuously scanning the sample over multiple measurements locations. The signals acquired at a fixed pump-probe time delay from a plurality of measurements locations has sufficient information and sensitivity to discriminate the presence or absence of a buried structure, such as a void, inclusion or solid structure, in a sample. The pump and probe beams may be focused in a line shaped illumination spot that is oriented orthogonally to that direction of travel during the scan, and a multi-channel linear detector array may detect signals at a plurality of locations along the line shaped illumination spot. Non-acoustic transient perturbations may be detected using two fixed pump-probe delay times.

A measuring device can detect and image buried structures, such as voids, in a sample based on the polynomial fit of the time resolved transient signals at a plurality of locations. A pulsed laser beam (pump beam) is used to irradiate the sample at a plurality of locations. The sample may include non-metallic, optically transparent layers that do not produce acoustic signals in response to the pump beams. Non-acoustic transient signals are detected using a probe beam at the plurality of locations. The buried structures are detected and imaged based on feature analysis (e.g., principal component decomposition, or polynomial fit, or other) of the non-acoustic transient signals at the plurality of locations.

A measuring device detects buried structures in a sample, such as voids or other underlying structures, based on an instantaneous signal difference determined from a single signal acquisition. The single signal acquisition is produced using a series of primary pump pulses and series of secondary pump pulses, which are intensity modulated and opposite in phase. The primary pump pulses and secondary pump pulses are combined to form a pump beam that is incident on the sample causing transient perturbations in material in the sample. Probe pulses are likewise incident on the sample and each probe pulse is modulated by the combined transient perturbations caused by a preceding primary pump pulse and a preceding secondary pump pulse. A series of reflected probe pulses are detected and demodulated to determine an instantaneous signal difference produced in response to the combined primary and secondary pump pulses, from which the buried structure is detected.

Mixed sensor array devices are provided herein. Mixed sensor arrays as described herein include acoustic energy generating elements and optical fiber based acoustic sensors. Optical fiber based sensors may optical structures responsive to physical parameters including acoustic signals, pressure, and temperature, and are configured to detect and receive acoustic signals and other physical parameters and provide associated optical signals to a system for processing and interpretation to implement tracking, location, imaging, and other sensing capabilities. Optical fiber based sensors provided herein may be disposed at ends of or along the length of optic fibers. Optical fiber based sensors may be included within various devices, including, for example, medical devices.

A transponder is used for tracking a position of a distal end of a medical device in an ultrasound image and/or enhancing an ultrasound image.