Power meter

The DBS electrodes were connected to a stimulator (Master-8 Programmable Stimulator, AMPI, Jerusalem, Israel), which delivered electrical pulses (pulse width = 60 μs, intensity = 100 μA) at specific frequencies based on the experimental design. The electrodes of the sham group were not connected to the stimulator, and therefore, the animals in this group did not receive any stimulation.
Blue (465 nm, 30 Hz, 10 ms, 10 mW) or yellow (589 nm, continuous, 10 mW) laser light was delivered using an optical stimulation system (IOS-465/589, RWD Instruments). For the negative control group, the parameters of the laser were adjusted to be the same as those used in the experimental group. The power of the laser was adjusted to approximately 10 mW, as measured using a power meter (Thorlabs).

Before the scattering measurement, a-Si:H NPs were drop coasted on a bare glass substrate. An inverted microscope (Ti-E, Nikon) with a spectrograph (Andor), an EMCCD (Andor) and a halogen white light source (12 V, 100 W) was employed to measure the scattering spectra of single a-Si:H NPs on the bare glass substrate^{18 (link),19 (link)}. Raman spectra of a-Si:H NPs were measured by the Witec Micro-Raman Spectrometer. A UV-VIS-NIR spectrometer (Ocean Optics) was used to measure the transmission of a-Si:H NPs in ethanol. An epi-fluorescence illuminator (mercury lamp, Nikon) and bandpass filters (central wavelength: 350 nm (UV) and 540 nm (green), bandwidth: 50 nm (UV) or 25 nm (green)) are used to generated UV and green light. The maximum power of UV and green light was measured by a power meter (Thorlabs). Since the mercury lamp is an incoherent light source and the incident light covers the whole rear aperture of the objective, the beam spot diameter used to calculate the incident light intensity is obtained by: d_spot = d_aperture/magnification, where d_aperture is the diameter of the objective rear aperture and equal to 6.5 mm and magnification is 100 times.

A laser (473 nm, Opto Engine LLC, Midvale, UT) was connected via a fiber collimator to a 1 meter fiber-connector (Ø200 µm core, 0.34 NA, Opto Engine LLC, Midvale, UT) coupled to a 3 meter long multimodal optical fiber (Ø200 µm core, 0.39 NA, ThorLabs, Newton, NJ), which was attached to the implanted fiber-optic ferrule. The intensity at the end of the patch cable was measured by a power meter (Thorlabs, Newton, NJ) and set at 12 mW. This accounts for a measured 20% power loss due to the coupling of the implanted ferrule, resulting in an estimated 10 mW at the infralimbic cortex. Timing of the laser pulse sequence was controlled by an Arduino Uno R3 microcontrol board (Arduino, Ivrea, Italy) and Processing 3.0 software platform. The TTL laser pulse train (frequency = 25 Hz, number of pulses = 4, pulse duration = 5 ms) was selected based on prior work showing mice learn to self-stimulate under these parameters (Yang and Ikemoto. Rewarding effects of optogenetic stimulation of the medial prefrontal cortex and adjacent regions in mice. SFN abstract, 2014).

The optical characterization of the fabricated sample was performed using an end-fire measurement set up³³ . Individual alignment procedures for each wavelength are carried out, using the Yenista Optics TLS, for Port A at 1530 nm, and a diode laser from Eblana Photonics for Port B at 1653.7 nm. The light generated is fed to an aspheric lens (10 ×) through optical fiber and a polarizing beam-splitter (PBS) is used to filter out the TM components. At this stage, the light is coupled to the device using a 60 × lens. A symmetrical arrangement is carried out to collect output. The alignment is achieved by maximizing the output power, derived from W_o, using a Thorlabs power meter. Following the alignment process, the TLS is replaced with an Amonics ALS broadband light source, while the diode laser is substituted with an Amonics ASLD super luminescent source. The resulting W_o transmittance spectrum for each port is separately collected using a Yenista Optics Optical Spectrum Analyzer (OSA).