Kun-Yii Tu

Demonstration of a Fourth-Order Pole-Zero Optical Filter Integrated Using CMOS Processes

We demonstrate a compact fully tunable narrowband fourth-order pole-zero optical filter that is fabricated in a silicon complementary-metal-oxide-semiconductor foundry. The filter is implemented using silicon on oxide channel waveguides and consists of a Mach-Zehnder interferometer with two ring resonator all-pass filters (APFs) on each arm. The filter architecture is based on the sum and difference of the APFs responses. The ring resonators introduce a nonlinear phase response in each arm that allows carving narrow frequency bands out of a broad spectrum. In this paper, we demonstrate a 3-dB filter bandwidth of 1.0 GHz with a stopband rejection of better than 25 dB. The filter free spectral range is 16.5 GHz. Thermooptic phase shifters are used to tune the filter. As silicon has a large thermooptic coefficient compared to silica, the demonstrated filter requires a low tuning power of less than 300 mW. In addition, this filter is compact with dimensions 25 times smaller than the same filter would be if it were made using standard silica on silicon waveguides with a 0.8% step index contrast

CMOS-Compatible Si-Ring-Assisted Mach–Zehnder Interferometer With Internal Bandwidth Equalization

We demonstrate, to the best of our knowledge, the first electrooptic ring-assisted Mach-Zehnder interferometric (RAMZI) modulator in a CMOS-compatible technology. The RAMZI modulator is manufactured on a CMOS-compatible platform and entirely fabricated in a commercial CMOS foundry. We demonstrate a small-signal 3-dB bandwidth >15 GHz in a silicon-based carrier-depletion modulator with a 2-V·cm V¿L product, which is approximately two times smaller than previously reported. We achieved a 10-Gb/s eye diagram with a 2-dB extinction ratio using a 4-Vp-p drive in a modulator with a 680-¿m optic/RF interaction region. In addition, we demonstrate internal bandwidth equalization within the tunable CMOS-compatible RAMZI modulator, and discuss the optical carrier and modulation sideband response, and relaxation characteristics that lead to this behavior within resonant modulators.

Internal Bandwidth Equalization in a CMOS-Compatible Si-Ring Modulator

Bandwidth equalization using a simple complementary metal-oxide-semiconductor-compatible tunable silicon-ring modulator is shown. We demonstrate >35-GHz small signal bandwidth and use the resonator to mitigate bandwidth limitations from other measurement system components. Configuring the optical carrier to be off resonance within the ring free-spectral range allows high-frequency enhancement and low-frequency suppression of the S21 parameter to achieve system response equalization. Our results suggest that the carrier and modulation sidebands can have very different transient characteristics within the ring modulator.

12.5-GHz optically sampled interference-based photonic arbitrary waveform Generator

This work presents an actively sampled photonic arbitrary waveform generator based on differential lithium-niobate electrooptic modulators. Ultralow timing jitter 1550-nm mode-locked laser time samples three serially connected Mach-Zehnder modulators, which are driven by six 12.5-Gb/s signals. This equivalent of photonic digital-to-analog converter allows for synthesis of high-quality arbitrary waveforms (>30-dB spurious-free dynamic range) over Nyquist bandwidth without loss of performance.

Waveguide-Integrated Ge p-i-n Photodetectors on SOI Platform

We demonstrate a fully CMOS processed Ge p-i-n photodetector integrated with a Si waveguide on a SOI platform with a high responsivity of 1.0 A/W at lambda=1520 nm, and a 3 dB bandwidth of >4.5 GHz measured at lambda=1550 nm

Linear phase-and-frequency-modulated photonic links using optical discriminators.

We report our experimental results for linear analog optical links that use phase or frequency modulation and optical discrimination. The discriminators are based on two architectures: a cascaded MZI FIR lattice filter and a ring assisted MZI (RAMZI) IIR filter. For both types of discriminators, we demonstrate > 6 dB improvement in the links third-order output intercept point (OIP3) over a MZM link. We show that the links have low second-order distortion when using balanced detection. Using high optical power, we demonstrate an OIP3 of 39.2 dBm. We also demonstrate 4.3dB improvement in signal compression.

Reconfigurable Linear Optical FM Discriminator

We present a reconfigurable optical discriminator filter for frequency modulated microwave-photonics link applications. The filter is based on a simplified ring-assisted Mach-Zehnder interferometer configuration. It enables conversion of a highly linear frequency to amplitude modulation. Operations in a fixed bandwidth (BW) of 30 GHz and a tunable bandwidth from 10 to 30 GHz are achieved using third- and fifth-order filters. A balanced frequency discrimination architecture with electronically reconfigurable transfer characteristics is demonstrated. We measured a output-third order intercept point (OIP3) linearity improvement over that of a dual-output Mach-Zehnder.

Tunable Narrowband Optical Filter in CMOS

We demonstrate a compact, fully tunable, narrowband (1GHz) 4thorder pole/zero optical filter that is fabricated in a silicon complementary metal oxide semiconductor foundry.

CMOS Compatible Guided-Wave Tunable Optical Equalizer

A compact 4th-order pole-zero optical filter fabricated entirely in a silicon complementary metal-oxide semiconductor foundry is configured as a tunable optical equalizer. Equalization of a bandwidth-limited 10-Gb/s signal is demonstrated with a single voltage control.

A Tunable Microwave-Photonic Notch Filter Fabricated in CMOS Silicon

We present a fully-tunable multi-stage narrowband (625 MHz) optical notch filter that is fabricated in a silicon complementary metal oxide semiconductor foundry. Using this device, a method to cancel undesired bands (910 MHz) in microwave-photonic systems is demonstrated.