Search

We present direct UV-written waveguides and Bragg gratings operating at 780 nm. By combining two gratings into a Fabry-Perot cavity we have devised and implemented a novel and practical method of measuring the group delay of Bragg gratings.

A path-folded infrared image spectrometer with five sub-gratings and five linear-array detectors was applied to a broadband optical monitoring (BOM) system for thin film deposition. Through in situ BOM, we can simultaneously acquire the thickness and refractive index of each layer in real time by fitting the measured spectra, and modify the deposition parameters during deposition process according to the fitting results. An effective data processing method was proposed and applied in the BOM process, and it shortened the data processing time and improved the monitoring efficiency greatly. For demonstration, a narrow band-pass filter (NBF) at 1540 nm with ~10 nm full width at half-maximum (FWHM) had been manufactured using the developed BOM system, and the results showed that this BOM method was satisfying for monitoring deposition of thin film devices.

The temperature dependence of the resonant wavelength of vertically coupled microring resonator can be controlled via internal stress caused by the thermo-optic and photo-elastic effects. In the case of strong internal stress, a polarization-independent microring resonator can be realized by controlling the device surface temperature using a heater module; the temperature dependence of TE and TM polarizations are different due to the internal stress and thus manipulating temperatures, the resonant wavelengths for TE and TM can be equalized at a specific temperature. In this study, the UV trimming of polarization-independent wavelength was demonstrated using UV-sensitive SiON as a core material. The temperature dependence of TE polarization was almost athermalized and that of TM was made negative by controlling internal stress. As a result, the simultaneous realization of the UV trimming and the polarization-independent microring was made possible more easily than before; the UV trimming can be done at room temperature due to the athermalized resonant wavelength for TE polarization.

We propose a scheme to induce transparency in one-dimensional disordered multilayers which are composed of negative permittivity and negative permeability metamaterials. First, analytical expressions for transparency condition are derived exactly, providing us a picture that complete tunneling in such kind of multiple-resonance system can be achieved if exponentially growing waves can compensate exponentially decaying waves. Second, a compensating method is used to realize this idea, and both simulations and experiments are performed in the microwave regime to confirm the theoretical analysis. Last, we have a discussion on how the coupling of resonances affects the transport properties of samples.

We present a planar design of a metamaterial exhibiting electromagnetically induced transparency that is amenable to experimental verification in the microwave frequency band. The design is based on the coupling of a split-ring resonator with a cut-wire in the same plane. We investigate the sensitivity of the parameters of the transmission window on the coupling strength and on the circuit elements of the individual resonators, and we interpret the results in terms of two linearly coupled Lorentzian resonators. Our metamaterial designs combine low losses with the extremely small group velocity associated with the resonant response in the transmission window, rendering them suitable for slow light applications at room temperature.

A femtosecond fiber laser was applied to fabricate broadband directional couplers inside bulk glass for general power splitting application in the 1250 to 1650-nm wavelength telecom spectrum. The broadband response was optimized over the 400-nm bandwidth by tailoring the coupling strength and the waveguide interaction length to balance the differing wavelength dependence of the straight interaction and bent transition regions. High spatial finesse of the femtosecond-laser writing technique enabled close placement (approxiamtely 6 microm) of adjacent waveguides that underpinned the wavelength-flattened broadband response at any coupling ratio in the 0% to 100% range. The spectral responses were well-represented by coupled mode theory, permitting simple design and implementation of broadband couplers for bulk 3D optical circuit integration.