Leaf A. Jiang

Noise of mode-locked semiconductor lasers

Analytical expressions for the amplitude, frequency, timing, and carrier phase noise of mode-locked laser diodes (MLLDs) are derived. It is found both experimentally and theoretically that carrier dynamics contribute to the total noise of MLLDs. In addition, we demonstrate how to capture the high-frequency timing jitter with optical cross correlations.

Quantum-limited noise performance of a mode-locked laser diode

Low-noise operation of a 9-GHz hybridly mode-locked laser diode is demonstrated. The integrated timing jitter was 47 fs (10 Hz to 10 MHz) and 86 fs (10 Hz to 4.5 GHz), with a pulse width of 6.7 ps. The noise performance as a function of filter bandwidth and oscillator noise is also addressed.

Measuring timing jitter with optical cross correlations

The use of optical cross correlations for characterizing timing jitter is investigated. Applications, limitations, and correspondence to radio frequency measurements are presented and clarified. The probability density function of the timing jitter of semiconductor mode-locked lasers is deconvolved from the cross-correlation measurements with the aid of pulse characterization techniques.

Timing jitter eater for optical pulse trains.

Using a single phase modulator and dispersive fiber, we demonstrate a 12-dB reduction in the phase noise of a train of 6.5-ps pulses at a repetition rate of 10 GHz. A prechirp fiber is shown to improve performance.

Observation of quantum-limited timing jitter in an active, harmonically mode-locked fiber laser

We report on the observation of quantum-limited timing jitter in a harmonically mode-locked soliton fiber laser with an ultralow-noise local oscillator. The effects of amplitude and phase modulation on the spectrum are described and compared with theory.

Ultralow-jitter, 1550-nm mode-locked semiconductor laser synchronized to a visible optical frequency standard

Using high-bandwidth feedback, we have synchronized the pulse train from a mode-locked semiconductor laser to an external optical atomic clock signal and achieved what is to our knowledge the lowest timing jitter to date (22 fs, integrated from 1 Hz to 100 MHz) for such devices. The performance is limited by the intrinsic noise of the phase detector used for timing-jitter measurement. We expect such a highly stable device to play an important role in fiber-network-based precise time/frequency distribution.

Self-stabilized passive, harmonically mode-locked stretched-pulse erbium fiber ring laser

We have studied a passive, harmonically mode-locked stretched-pulse erbium fiber ring laser with net positive dispersion that is self-stabilized by gain depletion and electrostriction. Periodic pulses with supermode suppression of >75 dB and picosecond jitter are achieved. The pulses are compressible to 125 fs by external chirp compensation. The repetition rate is 220 MHz, and the average power is as high as 80 mW.

Semiconductor mode-locked lasers as pulse sources for high bit rate data transmission

AbstractSemiconductor mode-locked lasers are evaluated as pulse sources for high bit rate data transmission. This chapter describes the requirements of OTDM sources for high bit rate data transmission, compares various OTDM source technologies, describes three semiconductor mode-locked laser cavity designs, explains the impact of timing jitter and amplitude noise on OTDM performance, illustrates how to characterize noise of OTDM sources using rf and optical techniques, shows how to interpret the noise measurements, and finally discusses semiconductor mode-locked laser cavity optimizations that can achieve low noise performance.

Timing jitter reduction in modelocked semiconductor lasers with photon seeding

We demonstrate improvement of the noise performance of a modelocked semiconductor laser using coherent photon seeding. We show that the timing jitter can be reduced without increasing the pulse width.

Heterodyne detection with a weak local oscillator

Heterodyne detection in the limit of weak (a few photons) local oscillator and signal power levels has been largely neglected in the past, as authors almost always assumed that the noise was dominated by the shot noise from a strong local oscillator. We present the theory for heterodyne detection of diffuse and specular targets at arbitrary power levels, including the case where the local oscillator power is only a few photons per coherent integration period. The theory was tested with experimental results, and was found to show good agreement. We show how to interpret the power spectral density of the heterodyne signal and how to determine the optimal number of signal and local oscillator photons per coherent integration.