Yu-Shan Juan

Photonic Generation of Broadly Tunable Microwave Signals Utilizing a Dual-Beam Optically Injected Semiconductor Laser

We propose and study photonic generation of broadly tunable microwave signals utilizing a dual-beam optically injected semiconductor laser. By injecting a slave laser with two detuned master lasers at the stable locking states, microwave signals with frequencies corresponding to the frequency spacing of the master lasers can be generated. Without the need for a microwave reference source, the dual-beam optical injection scheme has the advantages of low cost and less system complexity. Moreover, without the limitations of period-doubling bifurcation and Hopf bifurcation, by utilizing the period-one oscillation state with a single-beam injection scheme, the microwave signals generated with the proposed scheme have a much broader tuning range. In this paper, optical and power spectra of the microwave signals generated with the dual-beam optical injection scheme are compared with those generated with the optical mixing, the single-beam injection, and the unlocked dual-beam injection schemes. Generation of tunable microwave signals up to 120 GHz is demonstrated, which is currently limited by the locking range of the slave laser determined by the frequency difference between the Hopf (higher frequency) and the saddle node (lower frequency) bifurcation curves.

Microwave-frequency-comb generation utilizing a semiconductor laser subject to optical pulse injection from an optoelectronic feedback laser

Microwave frequency combs are generated by optically injecting a semiconductor laser (slave) with repetitive pulses from an optoelectronic feedback laser (master). By varying the delay time, regular pulsing states with different pulsing frequencies are generated in the master laser. The pulsing output is then optically injected into the slave laser to produce desired microwave frequency combs. Microwave frequency combs with broad bandwidths and low nonharmonic spurious noise are demonstrated experimentally. To analyze their stabilities and spectral purities, single-sideband phase noise of each microwave frequency comb line is measured. Noise suppression of the microwave frequency comb relative to the injected regular pulsing state is also investigated.

Ultra broadband microwave frequency combs generated by an optical pulse-injected semiconductor laser.

We have demonstrated and characterized the generation of ultra broadband microwave frequency combs with an optical pulse-injected semiconductor laser. Through optical pulse injection, the microwave frequency combs generated in the slave laser (SL) have bandwidths greater than 20 GHz within a +/-5 dB amplitude variation, which is almost 3-fold of the 7 GHz relaxation oscillation frequency of the laser used. The line spacing of the comb is tunable from 990 MHz to 2.6 GHz, determined by the repetition frequency of the injection optical pulses produced by the master laser (ML) with optoelectronic feedback. At an offset frequency of 200 kHz, a single sideband (SSB) phase noise of -60 dBc/kHz (-90 dBc/Hz estimated) in the 1(st) harmonic is measured while a noise suppression relative to the injected regular pulsing state of the ML of more than 25 dB in the 17(th) harmonic is achieved. A pulsewidth of 29 ps and a ms timing jitter of 18.7 ps are obtained in the time domain for the microwave frequency comb generated. Further stabilization is realized by modulating the ML at the fundamental frequency of the injected regular pulsing state. The feasibility of utilizing the generated microwave frequency comb in frequency conversion and signal broadcasting is also explored. The conversion gain of each channel increases linearly as the signal power increases with a ratio of about 0.81 dB/dBm.

Demonstration of ultra-wideband (UWB) over fiber based on optical pulse-injected semiconductor laser

We experimentally demonstrated the ultra-wideband (UWB) signal generation utilizing nonlinear dynamics of an optical pulse-injected semiconductor laser. The UWB signals generated are fully in compliant with the FCC mask for indoor radiation, while a large fractional bandwidth of 93% is achieved. To show the feasibility of UWB-over-fiber, transmission over a 2 km single-mode fiber and a wireless channel utilizing a pair of broadband antennas are examined. Moreover, proof of concept experiment on data encoding and decoding with 250 Mb/s in the optical pulse-injected laser is successfully demonstrated.

High-frequency microwave signal generation in a semiconductor laser under double injection locking

We numerically investigate high-frequency microwave signal generation utilizing a double injection locking technique. A slave laser (SL) is strongly injected by a master laser 1 (ML1) and a master laser 2 (ML2) optically. Stable locking states are observed when the SL is subject to optical injection by either the ML1 or the ML2 individually. By utilizing the hybrid scheme consists of double optical injections, the advantages of each individual dynamical system are added and enhanced. Comparison of the performances of the spectral width, power fluctuation, and frequency tunability between the signal generated in the double injection locking scheme and the similar period-one (P1) oscillation signal generated in a conventional single injection scheme is studied. A 3-fold linewidth reduction is achieved by utilizing the double injection locking scheme benefitted by the strong phase-locking and high coherence when operating at the stable injection locking state. Moreover, for the double injection locking scheme, a wide continuous tuning range of more than 100 GHz is obtained by adjusting the detuning frequency of the two master lasers. The performances of narrow linewidth, wide tuning range, and frequency continuity show the great advantages of the high-frequency microwave signal generated by the double injection locking technique.

High-frequency microwave signal generation in a semiconductor laser based on double injection locking

We numerically investigate the characteristics of high-frequency microwave signal generation by double injection-locking in a semiconductor laser. Performances of 60 GHz continuous tuning range, less than 5 dB power fluctuation, and narrow linewidth are achieved.

Demonstration of arbitrary channel selection utilizing a pulse-injected semiconductor laser with a phase-locked loop

An arbitrary channel selection system based on a pulse-injected semiconductor laser with a phase-locked loop (PLL) is experimentally demonstrated and characterized. Through optical injection from a tunable laser, channels formed by the frequency components of a microwave frequency comb generated in the pulse-injected semiconductor laser are individually selected and enhanced. Selections of a primary channel at the fundamental frequency of 1.2 GHz and a secondary channel in a range from 10.8 to 18 GHz are shown, where the selection is done by adjusting the injection strength from the tunable laser. Suppression ratios of 44.5 and 25.9 dB between the selected primary and secondary channels to the averaged magnitude of the unwanted channels are obtained, respectively. To show the spectral quality of the pulse-injected laser, a single sideband (SSB) phase noise of -60 dBc/kHz at an offset frequency of 25 kHz is measured. Moreover, the conversion gain between the primary and secondary channels and the crosstalk between the selected channels to the adjacent unwanted channels are also investigated. Without the need of expensive external modulators, arbitrary channel selection is realized in the proposed system where the channel spacing and selection can be continuously adjusted through tuning the controllable laser parameters.

Dynamical characteristics of a semiconductor laser injected by optical pulses with high repetition rate

The nonlinear dynamics of a semiconductor laser (slave laser) injected by optical pulses with high repetition rate are investigated experimentally. The pulses for injection are generated from a laser (master laser) subjected to either an optoelectronic feedback or an optical feedback. The repetition rates of the pulses are controlled by varying the delay time and the feedback strength of the feedback loop. By injecting the repetitive optical pulses of different intensities and repetition frequencies into another laser (slave laser), rich dynamical states including regular pulsations, frequency beatings, and chaotic pulsations are observed. Moreover, frequency-locked states with different winding number, the ratio of the main pulsation frequency of the slave laser and the repetition frequency of the injected pulses, are also found. Compared to a laser subject to a sine modulated optical injection, the linewidths of the high-order microwave components in the output spectrum of the slave laser are substantially narrower for the laser under repetitive optical pulse injection.

Demonstration of arbitrary channel selection utilizing a pulse-injected double phase-locked semiconductor laser

We demonstrate and characterize arbitrary channel selection utilizing both the double phase-locked and optical injection schemes experimentally. The double phase-locked scheme is realized by both optical injection and electrical modulation to the slave laser (SL) from a pulsed laser. The pulsed laser is generated by the semiconductor laser under optoelectronic feedback, which outputs repetitive pulse train with the repetition frequency controlled by the feedback delay time and feedback strength. When the SL subject to only the optical pulse injection from the pulsed laser, a broadband microwave frequency comb with amplitude variation ±5 dB in a 20 GHz range is generated. By further applying an electrical modulation to form a double phase-locked condition, a main channel can be selected accordingly. The advantages of large channel suppression ratio, system stabilization, and spurious noise reduction are obtained by using the double phase-locked technique. Moreover, by further applying an optical cw injection from a tunable laser, we demonstrate the selection of a secondary channel. A selection range of about 7.2 GHz is achieved by adjusting the cw injection strength. Average channel suppression between the main and secondary channels to the undesired channels with ratios of 41.8 and 25.9 dB are obtained, respectively. The single sideband (SSB) phase noise of -60 dBc/kHz (-90 dBc/Hz estimated) is achieved at offset frequencies of 25 and 200 kHz for the main and secondary channels, respectively. Demonstration of communication between the main and secondary channels is also demonstrated.

Demonstration of arbitrary channel selection in microwave frequency comb

We demonstrate arbitrary channel selection in microwave frequency comb by an optically-injected double phase-locked semiconductor laser. Suppression ratios of 41.8 and 25.9 dB between the main and secondary channels to the others are achieved.