Nicolas A. F. Jaeger

40 GHz electro-optic polarization modulator for fiber optic communications systems

A novel ultrahigh-speed electro-optic polarization modulator is introduced. The modulator uses a mode converter and a static polarization controller to change the output polarization state in a circular path, following a great circle, around the Poincaré sphere. Any two states on the Poincaré sphere can be connected. The mode converter is constructed using an AlGaAs ridge waveguide combined with slow-wave travelling wave electrodes. The travelling wave electrodes are designed to match the velocity of the electrical modulating signal, the data signal, to the optical carrier signal over a broad frequency range. This modulator demonstrates a 3 dB bandwidth in excess of 40 GHz. The polarization modulator exhibits extremely low differential group delay, on the order of a few 10s of femto-seconds, and low drive voltage, on the order of 5 V.

Narrow-band waveguide Bragg gratings on SOI wafers with CMOS-compatible fabrication process.

We demonstrate the design, fabrication and measurement of integrated Bragg gratings in a compact single-mode silicon-on-insulator ridge waveguide. The gratings are realized by corrugating the sidewalls of the waveguide, either on the ridge or on the slab. The coupling coefficient is varied by changing the corrugation width which allows precise control of the bandwidth and has a high fabrication tolerance. The grating devices are fabricated using a CMOS-compatible process with 193 nm deep ultraviolet lithography. Spectral measurements show bandwidths as narrow as 0.4 nm, which are promising for on-chip applications that require narrow bandwidths such as WDM channel filters. We also present the die-to-die nonuniformity for the grating devices on the wafer, and our analysis shows that the Bragg wavelength deviation is mainly caused by the wafer thickness variation.

Focusing sub-wavelength grating couplers with low back reflections for rapid prototyping of silicon photonic circuits

We demonstrate fully-etched fiber-waveguide grating couplers with sub-wavelength gratings showing high coupling efficiency as well as low back reflections for both transverse electric (TE) and transverse magnetic (TM) modes. The power reflection coefficients for the TE and TM modes have been significantly suppressed to -16.2 dB and -20.8 dB, respectively. Focusing grating lines have also been used to reduce the footprint of the design. Our sub-wavelength grating couplers for the TE and TM modes show respective measured insertion losses of 4.1 dB and 3.7 dB with 1-dB bandwidths of 30.6 nm (3-dB bandwidth of 52.3 nm) and 47.5 nm (3-dB bandwidth of 81.5 nm), respectively.

Uniform and Sampled Bragg Gratings in SOI Strip Waveguides With Sidewall Corrugations

We have demonstrated uniform and sampled Bragg gratings in silicon-on-insulator strip waveguides with symmetric sidewall corrugations. The fabrication is based on 193-nm deep ultraviolet lithography using a single mask. The measured reflection spectra of sampled gratings exhibit ten usable peaks spaced by 4.2 nm, and show good agreement with theoretical predictions.

Series-coupled silicon racetrack resonators and the Vernier effect: theory and measurement

Silicon-on-insulator racetrack resonators can be used as multiplexers in wavelength division multiplexing applications. The free spectral range should be comparable to the span of the C-band so that a maximum number of channels can be multiplexed. However, the free spectral range is inversely proportional to the length of the resonator and, therefore, bending losses can become non-negligible. A viable alternative to increase the free spectral range is to use the Vernier effect. In this work, we present the theory of series-coupled racetrack resonators exhibiting the Vernier effect. We demonstrate the experimental performance of the device using silicon-on-insulator strip waveguides. The extended free spectral range is 36 nm and the interstitial peak suppression is from 9 dB to 17 dB.

Integrated optics Pockels cell high-voltage sensor

The operation of the integrated optics Pockels cell and its application as a high-voltage power system sensor are explained. The effects of the waveguides geometry on the intrinsic phase-difference of the device is investigated. Properly biased devices as short as 7 mm have been fabricated and tested. While the piezoelectric behaviour of the sensor-heads affects the useful bandwidths of these devices, samples with bandwidths on the order of 1 MHz have been fabricated. Also, devices capable of reproducing lightning impulses with front-times as short as 0.5 /spl mu/s have been demonstrated. >

Silicon photonic grating-assisted, contra-directional couplers.

We demonstrate, in both theory and experiment, 4-port, electrically tunable photonic filters using silicon contra-directional couplers (contra-DCs) with uniform and phase-shifted waveguide Bragg gratings. Numerical analysis, including both intra- and inter-waveguide couplings, is performed using coupled-mode theory and the transfer-matrix method. The contra-DC devices were fabricated by a CMOS-photonics manufacturing foundry and are electrically tunable using free-carrier injection. A 4-port, grating-based photonic resonator has been obtained using the phase-shifted contra-DC, showing a resonant peak with a 3-dB bandwidth of 0.2 nm and an extinction ratio of 24 dB. These contra-DC devices enable on-chip integration of Bragg-grating-defined functions without using circulators and have great potential for applications such as wavelength-division multiplexing networks and optical signal processing.

Ultra-compact, flat-top demultiplexer using anti-reflection contra-directional couplers for CWDM networks on silicon

Wavelength-division-multiplexing (WDM) networks with wide channel grids and bandwidths are promising for low-cost, low-power optical interconnects. Wide-bandwidth, single-band (i.e., no free-spectral range) add-drop filters have been developed on silicon using anti-reflection contra-directional couplers with out-of-phase Bragg gratings. Using such filter components, we demonstrate a 4-channel, coarse-WDM demultiplexer with flat passbands of up to 13 nm and an ultra-compact size of 1.2 × 10(-3) mm(2).

High-voltage sensor employing an integrated optics Mach-Zehnder interferometer in conjunction with a capacitive divider

Such devices would be useful for monitoring line voltages in, for example, SF/sub 6/ gas-insulated bus ducts. The theory of the devices is described and the results of tests on a laboratory prototype are presented. Furthermore, the design of a device monolithically integrating a capacitive divider and an integrated-optics Mach-Zehnder interferometer is proposed. >

Contradirectional couplers in silicon-on-insulator rib waveguides

We demonstrate contradirectional couplers in silicon-on-insulator rib waveguides using a CMOS compatible technology, in which a periodic dielectric perturbation is introduced in the coupling region between two different-sized rib waveguides. This structure enables high fabrication tolerances for narrow-bandwidth add-drop filters, using commercially available deep-ultraviolet lithography, that do not suffer from having a free spectral range. The simulation using coupled-mode theory and mode-profile calculations shows good agreement with experiment. A narrow bandwidth of 0.35 nm and a low loss of less than 1 dB have been achieved experimentally.