Patterned photostimulation via visible-wavelength photonic probes for deep brain optogenetics

Optogenetic methods developed over the past decade enable unprecedented optical activation and silencing of specific neuronal cell types. However, light scattering in neural tissue precludes illuminating areas deep within the brain via free-space optics; this has impeded employing optogenetics universally. Here, we report an approach surmounting this significant limitation. We realize implantable, ultranarrow, silicon-based photonic probes enabling the delivery of complex illumination patterns deep within brain tissue. Our approach combines methods from integrated nanophotonics and microelectromechanical systems, to yield photonic probes that are robust, scalable, and readily producible en masse. Their minute cross sections minimize tissue displacement upon probe implantation. We functionally validate one probe design in vivo with mice expressing channelrhodopsin-2. Highly local optogenetic neural activation is demonstrated by recording the induced response—both by extracellular electrical recordings in the hippocampus and by two-photon functional imaging in the cortex of mice coexpressing GCaMP6

Wavelength locking of silicon photonics multiplexer for DML-based WDM transmitter

We present a wavelength locking platform enabling the feedback control of silicon (Si) microring resonators (MRRs) for the realization of a 4 × 10 Gb/s wavelength-division-multiplexing (WDM) transmitter. Four thermally tunable Si MRRs are employed to multiplex the signals generated by four directly modulated lasers (DMLs) operating in the L-band, as well as to improve the quality of the DMLs signals. Feedback control is achieved through a field-programmable gate array controller by monitoring the working point of each MRR through a transparent detector integrated inside the resonator. The feedback system provides an MRR wavelength stability of about 4 pm (0.5 GHz) with a time response of 60 ms. Bit error rate (BER) measurements confirm the effectiveness and the robustness of the locking system to counteract sensitivity degradations due to thermal drifts, even under uncooled operation conditions for the Si chip

Photonic platform and the impact of optical nonlinearity on communication devices

It is important to understand properties of different materials and the impact they have on devices used in communication networks. This paper is an overview of optical nonlinearities in Silicon and Gallium Nitride and how these nonlinearities can be used in the realization of optical ultra-fast devices targeting the next generation integrated optics. Research results related to optical lasing, optical switching, data modulation, optical signal amplification and photo-detection using Gallium Nitride devices based on waveguides are examined. Attention is also paid to hybrid and monolithic integration approaches towards the development of advanced photonic chips

Recent Advances in Wavelength-Division-Multiplexing Plastic Optical Fiber Technologies

This work has been supported by the Spanish Ministry of Economía y Competitividad under the grant TEC2012-37983-C03-02

Electronic Photonic Integrated Circuits and Control Systems

Photonic systems can operate at frequencies several orders of magnitude higher than electronics, whereas electronics offers extremely high density and easily built memories. Integrated photonic-electronic systems promise to combine advantage of both, leading to advantages in accuracy, reconfigurability and energy efficiency. This work concerns of hybrid and monolithic electronic-photonic system design. First, a high resolution voltage supply to control the thermooptic photonic chip for time-bin entanglement is described, in which the electronics system controller can be scaled with more number of power channels and the ability to daisy-chain the devices. Second, a system identification technique embedded with feedback control for wavelength stabilization and control model in silicon nitride photonic integrated circuits is proposed. Using the system, the wavelength in thermooptic device can be stabilized in dynamic environment. Third, the generation of more deterministic photon sources with temporal multiplexing established using field programmable gate arrays (FPGAs) as controller photonic device is demonstrated for the first time. The result shows an enhancement to the single photon output probability without introducing additional multi-photon noise. Fourth, multiple-input and multiple-output (MIMO) control of a silicon nitride thermooptic photonic circuits incorporating Mach Zehnder interferometers (MZIs) is demonstrated for the first time using a dual proportional integral reference tracking technique. The system exhibits improved performance in term of control accuracy by reducing wavelength peak drift due to internal and external disturbances. Finally, a monolithically integrated complementary metal oxide semiconductor (CMOS) nanophotonic segmented transmitter is characterized. With segmented design, the monolithic Mach Zehnder modulator (MZM) shows a low link sensitivity and low insertion loss with driver flexibility

Passband flattened binary-tree structured add-drop multiplexers using sion waveguide technology

When writing this introduction I saw the following press release on the Internet: “Nielsen//Netratings reports a record half billion people worldwide now have home internet access‿. The number of home users grew worldwide with 5 % over the last quarter of 2001. The growth was nearly doubled compared to Q3 2001. The growth in Europe was 4.9%, almost equal to the world growth. One in three households in Europe/Middle East and Africa have Internet access, compared with over half in the US. The Netherlands has 52 % of the households connected to the Internet and 82 % of the computers is connected to the Internet. Another press release also fromNielsen//Netratings was titled as “Broadband Usage Outpaces Narrowband for the first time.‿ 1.19 billion of the total 2.3 billion hours was spent by broadband surfers online in January 2002 in the US. The broadband time spent in January 2002 was 64 % higher than in January 2001. Nearly 21.9 million surfers (in the US) at-home accessed the Internet via broadband connection in January 2002 compared to 13.1 million in January 2001, a boost of 67% in one year time. So there is an unstoppable march towards broadband. (See www.nielsen-netratings.com) This demand can be fulfilled with the tremendous bandwidth of the optical fiber of 30 THz (1420-1670 nm). It is not possible to directly address this complete band, since the current maximum speed of the electronics and modulators is 40-100 GHZ. Wavelength division multiplexing (WDM) is used to divide the band in multiple sub bands. The spacing between the sub band channels is defined by the ITU grid. Common spacings between channels are 12.5, 25, 50, 100 and 200 GHz. The device that combines these channels onto one fiber is called a Multiplexer (Mux) and the device that does the opposite, spatial separation of frequency channels onto different fibers, is called a demultiplexer (Demux). When Mux and Demux are combined it is possible to select only one (or more) channel to be dropped or added and leaving the remaining channels undisturbed. Such a device is called an Add-drop multiplexer(ADM). Optical transmission systems 3.28 Tbit/s over a few hundred of kilometers[Nielsen 2000] or 2 Tbit/s over almost ten thousand kilometers [Yamada 2002] have already be reported