Ps Wide Pulses Research Articles

Ultrafast electro-optic time-frequency fractional Fourier imaging at the single-photon level.

The Fractional Fourier Transform (FRT) corresponds to an arbitrary-angle rotation in the phase space, e.g., the time-frequency (TF) space, and generalizes the fundamentally important Fourier Transform. FRT applications range from classical signal processing (e.g., time-correlated noise optimal filtering) to emerging quantum technologies (e.g., super-resolution TF sensing) which rely on or benefit from coherent low-noise TF operations. Here a versatile low-noise single-photon-compatible implementation of the FRT is presented. Optical TF FRT can be synthesized as a series of a spectral disperser, a time-lens, and another spectral disperser. Relying on the state-of-the-art electro-optic modulators (EOM) for the time-lens, our method avoids added noise inherent to the alternatives based on non-linear optical interactions (such as wave-mixing, cross-phase modulation, or parametric processes). Precise control of the EOM-driving radio-frequency signal enables fast all-electronic control of the FRT angle. In the experiment, we demonstrate FRT angles of up to 1.63 rad for pairs of coherent temporally separated 11.5 ps-wide pulses in the near-infrared (800 nm). We observe a good agreement between the simulated and measured output spectra in the bright-light and single-photon-level regimes, and for a range of pulse separations (20 ps to 26.7 ps). Furthermore, a tradeoff is established between the maximal FRT angle and optical bandwidth, with the current setup accommodating up to 248 GHz of bandwidth. With the ongoing progress in EOM on-chip integration, we envisage excellent scalability and vast applications in all-optical TF processing both in the classical and quantum regimes.

Design and Performance Analysis of a Picosecond Pulse Generator

A picosecond pulse generator is designed to generate a stable differentiated Gaussian (monocycle) waveform. The design approach to increasing the center frequency, bandwidth and peak-to-peak voltage, as compared to previously reported ultra-wideband (UWB) generators, is described. The 280 ps wide pulse achieves a 1:10 fractional bandwidth (FBW) ratio extending from 500 MHz to beyond 5 GHz at the -10 dB level. A measurement procedure is proposed for evaluating the jitter and noise performance of UWB pulse generators, and it is applied to the fabricated prototype. The procedure exploits jitter and noise definitions from high-speed digital electronics, which are adapted here for the jitter and noise evaluation of UWB pulse generators at microwave frequencies. The problems in obtaining the absolute and relative jitter of a UWB generator are discussed along with proposed solutions. The impact of the input trigger on the pulse stability is demonstrated through the dramatic improvement achieved by the integration of a jitter cleaner in the generator’s circuit.

Gigahertz repetition rate mode-locked Yb:KYW laser using self-assembled quantum dot saturable absorber

Fundamental mode-locking is achieved in a 1.036 GHz cavity using a semiconductor quantum dot saturable absorber mirror with a fast relaxation time component of down to 550 fs. The dispersive cavity delivers 1.7 ps wide pulses with spectra supporting sub-picosecond pulse durations and an M² of 1.3. An average output power of up to 339 mW at wavelengths around 1,032 nm is achieved and the saturable absorber’s damage threshold is identified as a limitation for further power scaling.

Optical properties and synchronously pumped mode-locked 1.73–2.10 μm tunable laser operation of [formula omitted] centers in KCl:Na +:O -2 crystals

Using synchronous pumping with ∽100 ps wide 1.32 μm Nd 3+:YAG laser pulses, we realize mode-locked KCl:Na +:O - 2 (F + 2) AH color center laser operation with nearly transform limited ∽5–10 ps wide pulses throughout a 1.73–2.10 μm tuning range. Pulses shorten continuously with increasing pump power levels. At maximum available pump power (∽2.3 W), average output power up to ∽380 mW is obtained in the peak of the tuning curve at 1.83 μm. Pulse shape and width measurements show that stable mode-locked operation is relatively insensitive towards cavity length detuning.

Very high amplitude, minimal chirp optical pulse generation at 1.55 μm using multicontact DFBs and an erbium doped fibre amplifier

A novel method of obtaining chirp minimised gain switched pulses of very high amplitude and contrast ratio is presented. 75 ps wide pulses at a 1.5 GHz repetition rate, with a −20 dB bandwidth of 4.7 A are demonstrated. This is the first time that chirp has been minimised for DFBs without the compromise of the pulse definition.

8 Gbit/s optical transmission with t.j.s. GaAlAs laser and p-i-n detection

Optical transmission at 8 Gbit/s has been performed with a t.j.s. laser and a low-impedance microstripline-mounted p-i-n diode. The laser was modulated with 100 ps wide pulses and no intersymbol interference was observed.