Sanja Zlatanovic

50-Gb/s Silicon Optical Modulator

Optical modulators formed in silicon are the keystone to many low cost optical applications. Increasing the data rate of the modulator benefits the efficiency of channel usage and decreases power consumption per bit of data. Silicon-based modulators which operate via carrier depletion have to the present been demonstrated at data rates up to 40 Gb/s; however, here we present for the first time optical modulation at 50 Gb/s with a 3.1-dB extinction ratio obtained from carrier depletion based phase shifter incorporated in a Mach-Zehnder interferometer. A corresponding optical insertion loss of approximately 7.4 dB is measured.

Parametric Photonic Channelized RF Receiver

A new class of photonic channelized radio-frequency (RF) receiver is proposed and demonstrated. The new device relies on generation of high fidelity signal copies by wavelength multicasting in a self-seeded, two-pump parametric mixer. Signal copying to widely spaced wavelengths enables channelization of the full RF bandwidth using a single periodic filter. The channelization uses freely tunable frequencies of newly generated copies and eliminates the need for construction of a dense, narrowband filter bank. The new concept is demonstrated by channelization of four subcarrier channels with 1-GHz spacing and greater than 20-dB extinction ratio between extracted channels.

Reconfigurable parametric channelized receiver for instantaneous spectral analysis

We propose and demonstrate a photonic approach to a reconfigurable channelized radio frequency (RF) receiver for instantaneous RF spectrum monitoring and analysis. Our approach relies on the generation of high quality copies of the RF input by wavelength multicasting in a 2- pump self-seeded parametric mixer and the use of off-the-shelf filtering element such as Fabry-Perot etalon and wavelength division demultiplexers. The parametric channelizer scheme trades frequency non-degeneracy of the newly generated copies for ease of filtering design. Self seeding scheme employed to wavelength multicast the original RF signal to a large number of copies enables easy reconfigurability of the device by simple tuning of the three input waves, i.e. seed and pumps. Channelizer operation to up to 15 GHz bandwidth and channel spacing of 500 MHz is demonstrated. Reconfigurability is verified by tuning the receiver operating bandwidth and channel spacing.

Transmission of 640-Gb/s RZ-OOK Channel Over 100-km SSMF by Wavelength-Transparent Conjugation

We report the first demonstration of 640-Gb/s return-to-zero ON-OFF keying channel transmission over a 100-km standard single-mode fiber link employing midspan phase conjugation. A frequency-degenerate conjugate field spanning more than 20 nm is created in a low-birefringence parametric mixer for the first time. Physical separation of the conjugate field from the original field is enabled by utilizing pump polarization nondegeneracy. Rigorous link characterization using a high-quality 640-Gb/s transmitter and a high-sensitivity receiver revealed error-free (bit error ratio <;10-9) performance, eliminating the need for impractical fiber length control or electronic signal processing. The compatibility of wavelength-transparent conjugation with spectrally inefficient channel implies that channels with higher bit rates and better spectral efficiency can also be compensated.

Continuous-wave four-wave mixing in cm-long Chalcogenide microstructured fiber

We present the experimental demonstration of broadband four-wave mixing in a 2.5 cm-long segment of AsSe Chalcogenide microstructured fiber. The parametric mixing was driven by a continuous-wave pump compatible with data signal wavelength conversion. Four-wave mixing products over more than 70 nm on the anti-stoke side of the pump were measured for 345 mW of pump power and 1.5 dBm of signal power. The ultrafast signal processing capability was verified through wavelength conversion of 1.4 ps pulses at 8 GHz repetition rate.

Third-order nonlinearity in silicon beyond 2350 nm

Measurement of the Kerr nonlinearity in silicon is reported in the 2350 nm to 2750 nm wavelength range, where three-photon absorption effect is present. The measurements confirm that the Kerr interaction strength is comparable to that in the near-infrared. The measured dispersion trend for the Kerr coefficient is consistent with that obtained using Kramers-Kronig relations. Three-photon absorption was measured, and its effect on the nonlinear figure of merit in silicon appears not to be as restrictive as that of two-photon absorption. The results identify silicon as a promising platform for parametric processes in mid-infrared spectral region.

Coherent Filterless Wideband Microwave/Millimeter-Wave Channelizer Based on Broadband Parametric Mixers

An essential capability in many applications, ranging from commercial, surveillance and defense, is to analyze the spectral content of intercepted microwave and millimeter-wave signals over a very wide bandwidth in real-time and with high resolution. A range of photonic schemes have been introduced for the real-time processing of wideband signals to overcome limitations of current conventional electronic frequency measurement approaches. Here, a novel microwave/millimeter-wave channelizer is presented based on a RF photonic front-end employing parametric wavelength multicasting and comb generation. This new technology enables a contiguous bank of channelized coherent I/Q IF signals covering extremely wide RF instantaneous bandwidth. High channel counts and wide RF instantaneous bandwidth are enabled by use of parametrically generated frequency-locked optical combs spanning >4 THz. Full field analysis capabilities of the coherent detection system are demonstrated by frequency domain analysis of 18 contiguous 1.2 GHz IF channels covering 15.5 GHz to 37.1 GHz input frequency range, and time and spectral domain analysis of a 75 GHz harmonically generated input signal. Sensitivity and dynamic range of the system are analyzed and discussed.

Short wavelength infrared frequency conversion in ultra-compact fiber device

Linear and nonlinear characteristics of devices using millimeter-scale spools of highly nonlinear fiber are experimentally investigated within 2000-2400nm spectral range. Coils with radius larger than 3.5 mm indicate that macro-bending induced radiation loss is negligible up to 2400nm. Devices with smaller diameter coiling resulted in macro-bending losses that dominate over micro-bending losses beyond 2200nm. A tunable short-wave infrared source was constructed using a coin-sized fiber module to demonstrate an efficient nonlinear conversion from 1.26 to 2.2 microm.

Phase-preserving parametric wavelength conversion to SWIR band in highly nonlinear dispersion stabilized fiber.

The first successful translation of a phase modulated optical signal over 80 THz, from the near infrared to the short-wave infrared (SWIR) band is demonstrated. A signal, phase-modulated at 10 Gbps, was received in an error-free manner in the SWIR(1.7-2.2 μm) band. A new class of highly nonlinear fiber with reduced dispersion fluctuation was utilized as the platform for this phase-preserving distant parametric conversion.

All-optical time-stretch digitizer

We propose and demonstrate an all-optical time-stretch digitizer for real-time capture of ultrafast optical signals, beyond the bandwidths achievable by electronics. This approach uniquely combines four-wave mixing and photonic time-stretch technique to slow down and record high-speed optical signals. As a proof-of-concept, real-time recording of 40-Gb/s non-return-to-zero on-off-keying optical data stream is experimentally demonstrated using a stretch factor of 54 and 1.5-GHz back-end electronic bandwidth. We also report on the observation of dispersion penalty and its mitigation via single-sideband conversion enabled by an optical bandpass filter. Our technique may provide a path to real-time capture of ultrahigh-speed optical data streams.