PHOTONIC INTEGRATED CIRCUIT

1 . A photonic integrated device comprising:

a photonic integrated chip (PIC) adapted to investigate blood flow at a portion of tissue of a user, said PIC comprising:

a laser having an optical output, or waveguide for guiding an optical output from an external laser, the optical output being split into a first optical component and a second optical component; wherein the first optical component is arranged to be transmitted to and generate speckle at the portion of tissue of the user;

the photonic integrated device further comprising:

one or more detectors, each detector configured to receive the speckle generated by the first optical component at the portion of tissue; and

one or more optical splitters optically coupling the second optical component to one or more respective input(s) of the one or more detectors;

wherein the photonic integrated device is further adapted to measure interference at the one or more detectors between a sample arm formed by the first optical component and a reference arm formed by the second optical component.

2 . The photonic integrated device of claim 1 , wherein the one or more detectors are located on the same PIC as the laser.

3 . The photonic integrated device of claim 1 , wherein the one or more detectors are located separately from the PIC.

4 . The photonic integrated device of claim 1 further comprising an ASIC or FPGA, said ASIC or FPGA configured to calculate temporal autocorrelation of a detected intensity.

5 . The photonic integrated device of claim 4 , wherein the ASIC or FPGA is configured to carry out speckle contrast measurements between images received by different detectors.

6 . The photonic integrated device according to claim 1 , further comprising a single mode waveguide or an aperture adapted to receive light from the portion of tissue of the user, said single mode waveguide or aperture placed in optical communication with a respective one of the one or more detectors.

7 . The photonic integrated device according to claim 1 , further comprising a multimode mode waveguide adapted to receive light from the portion of tissue of the user, said multimode mode waveguide placed in optical communication with a respective one of the one or more detectors.

8 . The photonic integrated device of claim 1 , wherein each detector receives only light from a single grain of speckle within a larger speckle pattern.

9 . The photonic integrated device of any claim 1 , wherein the PIC is a silicon photonics chip.

10 . The photonic integrated device of claim 1 , wherein the laser has a wavelength of operation of 1280 nm or more.

11 . The photonic integrated device of claim 1 , wherein the laser is a fixed wavelength laser.

12 . The photonic integrated device of claim 1 , wherein the laser is a tunable laser.

13 . The photonic integrated device of claim 1 , further comprising one or more additional lasers such that the PIC comprises a plurality of lasers.

14 . The photonic integrated device of claim 13 , wherein each laser of the plurality of lasers has a different wavelength or wavelength range of operation.

15 . The photonic integrated device of claim 13 , wherein the plurality of lasers are operated one laser at a time.