Slave Laser Diode Research Articles

Orbital Instability of Chaotic Laser Diode with Optical Injection and Electronically Applied Chaotic Signal

We numerically studied the chaotic dynamics of a laser diode (LD) system with optical injection, where a chaotic signal, which is generated by an LD with optical feedback, is applied to the drive current of the master LD. To quantify the orbital instability of the slave LD, the Lyapunov exponent was calculated as a function of the optical injection ratio between the master and slave LDs and the optical feedback ratio of the applied signal. We found that the Lyapunov exponent was increased and the orbital instability was enhanced by applying a chaotic signal when the inherent system without the applied signal was in a “window”. Next, we investigated the orbital instability of the slave LD in terms of statistical and dynamical quantities of the applied chaotic signal. The maximal value of the Lyapunov exponent for a certain range of the injection ratio was calculated and we showed that a chaotic pulsation is suitable for enhancing the orbital instability of the LD system. We then investigated chaos synchronization between the LDs. It is concluded that the orbital instability of an LD with optical injection can be enhanced by applying chaotic pulsation without chaos synchronization.

Amplification of a nanosecond laser pulse chain via dynamic injection locking of a laser diode.

We report a novel optical pulse generation method for high-speed wavelength switching of amplified nanosecond (ns) laser pulses resonant to atomic transitions. Under free-running conditions, a slave laser diode is blue-detuned with tens of GHz relative to the master laser. A nanosecond pulse chain generated by modulating the continuous-wave master laser with a fiber-pigtailed electro-optical intensity modulator is injected into the slave laser diode to fast switch the slave laser's wavelength back and forth. The output beam of the slave laser is filtered by a temperature-controlled etalon to get the amplified pulse chain. Based on our dynamic injection locking scheme, we produce an ns-scale square pulse chain with an effective ON/OFF ratio ∼108, considering at least the 60 dB scattering suppression by tuning the light-atom interactions with far off-resonance detuning and the 26.7 dB suppression ratio of the etalon. By studying the dynamic processes of injection locking, we determine the dependence of injection locking on both the injection power and the frequency detuning.

High-bandwidth transfer of phase stability through a fiber frequency comb.

We demonstrate phase locking of a 729 nm diode laser to a 1542 nm master laser via an erbium-doped-fiber frequency comb, using a transfer-oscillator feedforward scheme which suppresses the effect of comb noise in an unprecedented 1.8 MHz bandwidth. We illustrate its performance by carrying out coherent manipulations of a trapped calcium ion with 99 % fidelity even at few-μs timescales. We thus demonstrate that transfer-oscillator locking can provide sufficient phase stability for high-fidelity quantum logic manipulation even without pre-stabilization of the slave diode laser.

Precision and broadband frequency swept laser source based on high-order modulation-sideband injection-locking.

A precision and broadband laser frequency swept technique is experimentally demonstrated. Using synchronous current compensation, a slave diode laser is dynamically injection-locked to a specific high-order modulation-sideband of a narrow-linewidth master laser modulated by an electro-optic modulator (EOM), whose driven radio frequency (RF) signal can be agilely, precisely controlled by a frequency synthesizer, and the high-order modulation-sideband enables multiplied sweep range and tuning rate. By using 5th order sideband injection-locking, the original tuning range of 3 GHz and tuning rate of 0.5 THz/s is multiplied by 5 times to 15 GHz and 2.5 THz/s respectively. The slave laser has a 3 dB-linewidth of 2.5 kHz which is the same to the master laser. The settling time response of a 10 MHz frequency switching is 2.5 µs. By using higher-order modulation-sideband and optimized experiment parameters, an extended sweep range and rate could be expected.

Reusing Downstream Carrier in Colorless Laser Diode for Full-Duplex 64-QAM OFDM

Without the need of any inline data eraser, the downstream carrier is reused in an upstream colorless laser diode transmitter to demonstrate full-duplex bidirectional 64-QAM OFDM passive optical network (PON) at up to 18 Gb/s. Therein, the downstream signal is used to control the wavelength of upstream laser diode by injection locking, and the slave laser diode then generates the injection-locked carrier for carrying the upstream signal. Distributing the OFDM subcarriers into dual frequency regions for upstream (baseband at 0-3 GHz) and downstream (up-shifted band at 3-6 GHz) transmissions avoids the crosstalk and simplifies the full-duplex system. The downstream power splitting ratio of 60/40 is optimized for receiving/injection branches at user end. For the downstream 64-QAM OFDM data after propagating 25-km SMF, a sensitivity of received power at least -8.5 dBm is required to suppress the BER below 3.8 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> for the forward-error correction (FEC) criterion. When directly reusing the downstream carrier with unerased data to injection-lock the colorless laser diode, the 25-km SMF transmitted upstream 64-QAM OFDM data exhibits an SNR of 22.9 dB and an error vector magnitude of 4.1%, which provides a BER of 1.5 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> at a received power of -5.8 dBm. Such a downstream carrier reused colorless laser diode upstream transmitter with inline eraser-free operation has shown its applicability for full-duplex quadrature amplitude modulation orthogonal frequency-division multiplexing PON.

Characterizing passive coherent population trapping resonance in a cesium vapor cell filled with neon buffer gas

We present a pair of phase-locked lasers with a 9.2-GHz frequency difference through the injection locking of a master laser to the RF-modulation sideband of a slave diode laser. Using this laser system, a coherent population trapping (CPT) signal with a typical linewidth of ∼ 182 Hz is obtained in a cesium vapor cell filled with 30 Torr (4 kPa) of neon as the buffer gas. We investigate the influence of the partial pressure of the neon buffer gas on the CPT linewidth, amplitude, and frequency shift. The results may offer some references for CPT atomic clocks and CPT atomic magnetometers.

Widely Tunable Ultra-Wideband Signals Generation Utilizing Optically Injected Semiconductor Laser

We propose and experimentally demonstrate an approach to generate ultra-wideband (UWB) pulse based on period-one oscillation of semiconductor laser. The baseband UWB signal with 10-dB bandwidth of 5.59 GHz is generated when the gain-switched pulse train is injected into the slave laser diode. Moreover, the center frequency of the generated UWB signal can be continuously tuned and converted up to 19.53 GHz by adjusting the optical frequency detuning in optical domain directly.

Frequency domain analysis of the chaotic synchronization of injection-locked semiconductor lasers

The quality and degree of synchronization obtained between a chaotic master laser diode and a slave laser diode is usually assessed using a correlogram. This technique is known to accurately identify areas of good synchronization, but it is not able to elucidate why these regions exist. By using a complementary frequency domain technique, the response gain, we have been able to obtain further insight into the synchronization process. We show using numerical simulations that trends in synchronization quality evident in the injection-locking diagram are also present in the response gain. We also show that most of the spectral power is situated in a small band of frequencies close to the relaxation oscillation frequency of the master laser and that accurate reproduction of these frequency components in the slave laser is vital in achieving a good synchronization. We associate the variation in synchronization quality within the injection-locking regime to changes in the response gain profile induced by the optical injection from the master laser. Variations in the spectral profile of the response gain clearly delineate and explain the various regions seen in the correlation synchronization diagram.

All optical linearization technique of DFB‐LD based on optical injection locking for RoF system

AbstractA novel all optical linearization technique using optical injection locking is proposed for radio‐over‐fiber system. When slave laser diode (SLD) is operated under injection locking condition, the modulated optical signals from master laser diode (MLD) are suppressed by residual amplitude modulation suppression. However, these signals are not completely suppressed by imperfection of residual amplitude modulation suppression and remained in the cavity of SLD. By appropriately controlling the phase and amplitude of these signals to have out‐of phase and the same magnitude condition compared with those of direct modulated optical signals from SLD, the efficiency of linearization of DFB‐LD can be more enhanced by optical cancellation in the SLD. By using the proposed technique, 17 dB enhancement of carrier‐to‐interference ratio was experimentally achieved up to frequency response of DFB‐LD compared with that of free‐running case. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2403–2406, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22800

Optical Transmitter Using Side-Mode Injection Locking for High-Speed Photonic LANs

This paper discusses an optical transmitter in parallel transmission systems using variable wavelengths. We propose to apply side-mode injection locking using a Fabry-Pe/spl acute/rot laser to realize this transmitter. Important characteristics are the injection power required for single-mode lasing of a slave laser diode (LD) and its dependence on side mode m. This paper measures the required power as a function of m and proposes a new simple theory to explain the measured data. The linewidths of injection-locked LDs were experimentally investigated as a function of m. The relation between the linewidths of master and slave LDs were also measured. Finally, the paper describes fundamental transmission experiments at 1 Gb/s using an injection-locked LD to clarify the side-mode dependence of bit-error rate.

Injection-Locking of Blue Laser Diodes and Its Application to the Laser Cooling of Neutral Ytterbium Atoms

We present a simple, laser-diode-based ultraviolet light source with sufficient power and narrow linewidth. In this scheme, an injection-locking technique was applied, for the first time to our knowledge, to a GaN blue laser diode (LD). By injecting ∼5 mW output light of the external cavity laser diode (ECLD) into two free-running blue slave LDs, we could obtain an output power of over 30 mW from the injection-locked slave LDs. The characterisitics of the injection-locked slave LD were studied in detail. We also present an absolute frequency-locking scheme with about a 500 MHz locking bandwidth, where we achieved offset-locking of the frequencies of two ECLDs. As an interesting example of the application of these developments, we demonstrated laser cooling and trapping of ytterbium atoms.

Optical Cryptosystem Based on Synchronization of Hyperchaos Generated by a Delayed Feedback Tunable Laser Diode

We propose a method for encrypting a signal within the high dimensional chaotic fluctuations of the wavelength from a delayed feedback tunable laser diode. Decoding is performed remotely by using a slave laser diode fully synchronized with the master one. No additional synchronization channel is required.

Raman polarization-selective feedback schemes for all-optical microwave frequency standards

All-optical locking of the frequency difference between two laser diodes onto a Raman transition is demonstrated. The properties of Raman-type polarization spectroscopy are discussed and exemplified in the cases of the 3.036 GHz Raman resonance of the 85Rb D2 line. The generation of a polarization-selective Raman resonant optical feedback ensures the Raman optical locking of the slave diode laser onto the master oscillator.

Spectral stabilization of an InGaAsP semiconductor laser by injection-locking

This report presents both experimental and theoretical results about phase-locking and spectral purity transfer by light injection in InGaAsP semiconductor lasers. From an experimental point of view, only a few tens of nanowatts are sufficient to impose the injected beam frequency to the slave laser. To make injection-locking more confortable to study, the master laser frequency noise is reduced by resonant optical coupling to an external cavity. The master laser spectral purity transfer and the stability of the slave laser along the locking range are examined in detail. The spectral purity transfer between a monomode beam and a multimode mode laser is also studied. From a theoretical point of view, the nonlinear evolution of the phase-locking mechanisms over the three injection regimes is fully explained. In the multimode case, the spectral purity transfer is due to the saturation sharing between the spectral components of the gain. In the monomode case, the calculation of the frequency noise spectral density of the slave diode laser injected with a low frequency noise beam shows that the master laser spectral purity is fully transmitted to the slave laser up to a frequency which is proportional to the square root of the injected power. The final section presents two injection-locking based methods for measuring the Henry factor, and a comparison with evaluation from a method independent to injection-locking techniques.

Narrowband frequency control of an injection-locked diode-laser battery

The stability of an injection-locked DFB 1.5 μm diode laser is studied systematically. A master diode laser with high spectral purity is used to injection lock a similar diode laser. The spectral purity of the master laser is successfully transmitted to the slave diode laser. A numerical simulation fits the experimental results and gives exact simple interpretations of the behavior of the slave diode laser. Three regimes occur at different injection levels. The relaxation hole appearing on the locking range pattern, for medium and strong injection regimes, is fully explained and leads to a complete explanation of the stability of the slave diode laser. As a consequence, two possible determinations of the Henry α factor [1] are presented, with a 5% precision for one of them

Stability of an injection-locked DFB 1.5 μm semiconductor laser

The stability of an injection-locked DFB 1.5 μm diode laser is studied systematically. A master diode laser with high spectral purity is used to injection lock a similar diode laser. The spectral purity of the master laser is successfully transmitted to the slave diode laser. A numerical simulation fits the experimental results and gives exact simple interpretations of the behavior of the slave diode laser. Three regimes occur at different injection levels. The relaxation hole appearing on the locking range pattern, for medium and strong injection regimes, is fully explained and leads to a complete explanation of the stability of the slave diode laser. As a consequence, two possible determinations of the HENRY α factor [1] are presented, with a 5% precision for one of them

Mode locking of laser diodes by picosecond optical pulse synchronous pumping

Short optical pulse generation from an external-cavity laser diode (LD) by optical pulse pumping has been investigated for the first time. An optical pulse train (pulse duration ∼40 ps) generated by a gain-switched LD was injected into a LD with an external cavity (slave LD) which was biased just below the laser threshold. The wavelength of the injected optical pulse was chosen to be slightly shorter than that of the slave LD. When the repetition rate of the optical injection pulse was nearly equal to the round trip time of the external cavity, the slave LD showed stable mode locking with the shorter pulse duration (∼22 ps) than that of the pumping pulse. At both the upper and lower repetition rates, the pulse duration of the slave LD also became shorter than that of the pumping pulse.

Frequency stabilization of an AlGaAs laser diode by a Fabry-Perot interferometer locked to a laser beam frequency -locked to the D_2 line of a Cs atomic beam

An AlGaAs laser diode (slave laser) has been frequency-locked to a Fabry-Perot interferometer which is locked to a diode laser (master laser) beam frequency-locked to the D(2) line of a Cs atomic beam. Frequency-locking of the Fabry-Perot interferometer to the master laser beam frequency-locked to a resonance line of an atomic beam greatly improves its long-term frequency stability. Therefore, it substantially improves the slave laser diode frequency stability frequency-locked to it. The measured frequency stabilities show that the very high frequency stability of the D(2) line of a Cs atomic beam has been transferred to the slave laser by this frequency-locking system within 1.6 x 10(-11)(10s). This system can be used for building a network of diode lasers with high frequency stability.