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We demonstrate an electro-optic sampling technique for high-resolution acquisition of few-photon signals. The temporal features of a biphoton distribution are observed with 98 ps resolution using slow detectors with a response extending >1 ns.

We demonstrate high-speed detection of low-photon waveforms using slow off-the-shelf detectors. Using a detector with a distorted instrument response function spanning > 1 ns, we recover single photon waveforms at a resolution of 60 ps.

We introduce a novel method to controllably improve the performance of photonic quantum random number generators by using minimum information entropy per bit as a standalone design parameter.

We experimentally demonstrate intensity amplification of repetitive picosecond optical pulses with an input-to-output gain up to 5.5 dB using a passive Talbot amplifier. Through the dispersion-induced temporal Talbot effect, the amplifier uses electro-optic phase modulation and a low-loss dispersive medium to exploit and coherently redistribute the energy of the original pulse train into fewer, replica, amplified pulses. In addition, we show how our passive amplifier mitigates the pulse train timing-jitter and pulse-to-pulse intensity fluctuations above a specific cutoff frequency., 4 pages, 5 figures

The temporal Talbot effect comprises a set of self-imaging phenomena in which a pulse train undergoes various coherence revivals after propagation through a dispersive medium. Besides the intrinsic physical interest of the phenomenon itself, the effect has found practical applications in various scientific areas. In optical signal processing, the temporal Talbot effect has been used to multiply the repetition-rate of periodic pulse sequences by integer factors. Because it operates coherently on the frequencies that comprise a pulse train, the temporal Talbot effect has been shown to mitigate noise such as reduction of pulse-to-pulse timing jitter and amplitude variation, as well as real-time optical averaging. Recently, there has been renewed interest in the temporal Talbot effect due to its use in arbitrary repetition rate multiplication and division, not just integer multiplication. Arbitrary repetition-rate control is based on a suitable combination of temporal phase-modulation and spectral-phase filtering using temporal Talbot conditions. By adjusting the phase-modulation profile and group-velocity dispersion, the multiplication and division factors can be tuned to be any desired values- fractional or integer. One of the main advantages of this methodology compared to traditional approaches of repetition rate control is its energy efficiency. Because temporal and spectral phase filtering are lossless processes, pulse trains using Talbot-based repetition rate control only suffer insertion loss from the system. In this article, we first present an overview of the theory behind temporal Talbot effects and then review recent work on its application for realizing arbitrary control of the repetition-rate of periodic optical pulses. This platform enables the creation of simple, versatile optical pulse sources for diverse applications where customized repetition rates are necessary.

We introduce and experimentally demonstrate a new design for passive Talbot amplification of repetitive optical waveforms, in which the gain factor can be electrically reconfigurable. The amplifier setup is composed of an electro-optic phase modulator followed by an optical dispersive medium. In contrast to conventional Talbot amplification, here we achieve different amplification factors by using combinations of fixed dispersion and programmable temporal phase modulation. To validate the new design, we experimentally show tunable, passive amplification of picosecond optical pulses with gain factors from m = 2 to 30 using a fixed dispersive line (a linearly chirped fiber Bragg grating).

We propose and experimentally demonstrate the first design of a fiber-optics programmable base/sub-harmonic optical clock recovery circuit, involving a phase modulator and linear dispersion, in which the rate division factor can be electrically reconfigurable through the modulation driving waveform.

We show 3.0 ps pulses from 1877 nm to 2008 nm at variable repetition rates up to 18 GHz using time-lens compression of a tunable CW laser. The center wavelength is changed by tuning the CW seed laser, and the repetition rate is changed by electronically tuning the drive of the master RF clock. The repetition rate of 18 GHz represents a record speed for pulse generation in this spectral region. This simple all-fiber platform uses standard 1550 nm telecom components, offering a turn-key, flexible, robust alternative to pulse generation in the 2.0 μm region with both wavelength and repetition rate tunability.

We introduce a new design for Talbot-based passive amplifiers, involving temporal phase modulation and dispersion, in which the gain factor can be electrically reconfigurable. In particular, we show gain factors from m = 2 to 30 using a fixed dispersive line (FBG).

We experimentally demonstrate input-to-output gain in a Talbot amplifier, operating without using any active gain process, by recycling energy already stored in the input repetitive signal. We show a gain factor exceeding the total system loss by 5dB.

We propose and experimentally demonstrate repetition-rate multiplication of picosecond optical pulse trains by a fractional factor based on temporal self-imaging, involving temporal phase modulation and first-order dispersion. Multiplication factors of 1.25, 1.33, 1.5, 1.6, 1.75, 2.25, 2.33, and 2.5 are achieved with high fidelity from a mode-locked laser with an input repetition-rate between 10 and 20 GHz.

Amplification of signal intensity is essential for initiating physical processes, diagnostics, sensing, communications and measurement. During traditional amplification, the signal is amplified by multiplying the signal carriers through an active gain process, requiring the use of an external power source. In addition, the signal is degraded by noise and distortions that typically accompany active gain processes. We show noiseless intensity amplification of repetitive optical pulse waveforms with gain from 2 to ~20 without using active gain. The proposed method uses a dispersion-induced temporal self-imaging (Talbot) effect to redistribute and coherently accumulate energy of the original repetitive waveforms into fewer replica waveforms. In addition, we show how our passive amplifier performs a real-time average of the wave-train to reduce its original noise fluctuation, as well as enhances the extinction ratio of pulses to stand above the noise floor. Our technique is applicable to repetitive waveforms in any spectral region or wave system., The amplification of optical waveforms requires the use of an external power source. Here, using temporal self-imaging, the authors achieve passive amplification of repetitive optical signals by coherently adding identical waveform copies on top of one another at a lower repetition rate.

We show experimentally undistorted, intensity amplification of optical pulse waveforms with gain from 2 to ~20 without using active gain by recycling energy already stored in the input repetitive signal.

I generate 3.6 ps 10-GHz pulses at 1877 nm in an all-fiber package without mode-locking. To the best of my knowledge, this shows the highest repetition rate for all-fiber ultrafast pulse generation near 2.0 μm.

We demonstrate an all-optical tunable delay in fiber based on wavelength conversion, group-velocity dispersion, and wavelength reconversion. The device operates near 1550 nm and generates delays greater than 800 ps. Our delay technique has the combined advantages of continuous control of a wide range of delays from picoseconds to nanoseconds, for a wide range of signal pulse durations (ps to 10 ns), and an output signal wavelength and bandwidth that are the same as that of the input. The scheme can potentially produce fractional delays of 1000 and is applicable to both amplitude- and phase-shift keyed data.

Using time-lens compression in a loop configuration, we generate 516 fs pulses at 3.5 nJ pulse energy from a continuous-wave 1.55 mum source without mode locking. Just as a spatial lens can expand or focus a beam in space, so can a time-lens broaden or compress a pulse in time. By placing a time-lens in a loop, we maximize the efficiency of bandwidth generation by using one time-lens driven at low power to emulate a stack of many lenses. Our system is compact, is all fiber, and allows large tuning of the repetition rate and continuous tuning of the pulse width and center wavelength.

We demonstrate a method of generating short pulses at 1350 nm by exciting Cerenkov radiation in a higher-order-mode fiber with a 1064 nm femtosecond fiber laser. We measure a 106 fs, 0.66 nJ output pulse. Cerenkov radiation in fibers allows for energy transfer between a soliton and a dispersive wave, providing an effective and engineerable platform to shift the wavelength of a femtosecond source. With appropriate design of the higher-order-mode fiber, this method of generating short pulses at 1350 nm can be extended to other wavelengths and to higher pulse energies.

We demonstrate soliton self-frequency shift of more than 12% of the optical frequency in a higher-order mode solid, silica-based fiber below 1300nm. This new class of fiber shows great promise for supporting Raman-shifted solitons below 1300nm in intermediate energy regimes of 1 to 10nJ that cannot be reached by index-guided photonic crystal fibers or air-core photonic bandgap fibers. By changing the input pulse energy of 200fs pulses from 1.36 to 1.63nJ we observe Raman-shifted solitons between 1064 and 1200nm with up to 57% power conversion efficiency and compressed output pulse widths less than 50fs. Furthermore, due to the dispersion characteristics of the HOM fiber, we observe redshifted Cerenkov radiation in the normal dispersion regime for appropriately energetic input pulses.

In this tutorial, we will show several novel optical instruments using optical phase modulation, which is a common technique used in fiber optic communications for phase shift keying and chirped RZ transmission. We will cover the concept of space-time duality, time-lens for jitter compensation and pulse compression, time-prism for ultrafast tunable optical delay, and generation of effective negative nonlinear refractive index using electro-optic phase modulation for compensation of self-phase modulation. These device concepts are inspired by the rapid technological development in telecom, and demonstrate the great potential of applying telecom technologies to optical instrumentation.

We demonstrate a simple, all-fiber technique for removing nonlinear phase due to self-phase modulation in fiber-based chirped-pulse amplification (CPA) systems. Using a LiNbO3 electro-optic phase modulator to emulate a negative nonlinear index of refraction, we are able to remove 1.0 pi rad of self-phase modulation acquired by pulses during amplification and eliminate nearly all pulse distortion. Our technique is high speed, removes nonlinear phase on a pulse-to-pulse basis, and can be readily integrated into existing CPA systems.

We demonstrate an all-fiber, programmable, ultrafast optical delay line based on reversible frequency conversion by use of a time-prism pair. Using electro-optic phase modulators to provide the time-prism phase profile, we show a record scanning rate of 0.5 GHz and a delay range of 19.0 ps. Computer modeling suggests that aberration correction in the time-prism system can extend the delay range to 28.0 ps. Finally, limitations and potential improvement of our techniques are discussed.

A programmable, ultrafast optical delay line with a robust all-fiber configuration is demonstrated. A record scanning rate of 0.5 GHz with a delay range of 19 ps is achieved without any mechanical motion. In addition, we will discuss the challenges and future improvements.

A method and apparatus for generating a multi-wavelength pulse train use a technique referred to as time-lens compression. The time-lens is formed of a phase modulator in series with a dispersion element. In addition to pulse compression, this time-lens simultaneously displaces the pulses according to their center wavelengths, resulting in a temporally evenly spaced multi-wavelength pulse train. An aberration correction technique, based on the temporal analog of a spatial correction lens, can also be employed improve the quality of the compressed pulses. Through use of CW DFB lasers and electrooptic phase modulators, the all-fiber system allows complete tunability of temporal spacing, spectral profile and repetition rate.

We study and demonstrate the technique of simultaneous spatial and temporal focusing of femtosecond pulses, with the aim to improve the signal-to-background ratio in multiphoton imaging. This concept is realized by spatially separating spectral components of pulses into a "rainbow beam" and recombining these components only at the spatial focus of the objective lens. Thus, temporal pulse width becomes a function of distance, with the shortest pulse width confined to the spatial focus. We developed analytical expressions to describe this method and experimentally demonstrated the feasibility. The concept of simultaneous spatial and temporal focusing of femtosecond pulses has the great potential to significantly reduce the background excitation in multiphoton microscopy, which fundamentally limits the imaging depth in highly scattering biological specimens.