Master Laser Research Articles

Injection seeding in a dual-cavity gain-switched Ti:Sapphire laser

An experimental investigation of a pulsed tunable injection-seeding system pumped by a Nd:YAG laser is presented. The slave laser (SL) of the system is a gain-switched Ti:Sapphire laser with a dual-channel competitive cavity which consists of a main ring channel and an auxiliary linear one with different lengths. The use of this configuration results in full and reliable suppression of both the perturbing reverse radiation from the SL to the master laser (ML) and the broadband spectral background of the SL's ring channel. This is achieved irrespective of the ratio between the energies of the SL and ML, fluctuations of laser parameters, and spectral detuning. We take advantage of the gain-switched regime of the Ti:Sapphire laser to avoid simultaneous competition between the SL's channels; this allows us to obtain spectrally pure, unidirectional output radiation with high seeding and overall efficiency. The principle of operation of the ring-linear-cavity Ti:Sapphire slave laser provides a natural optical isolation between the SL and ML; this makes such lasers suitable for use as regenerative amplifiers when seeded by single-frequency diode lasers as well as in chirped-pulse-amplification systems to amplify ultrashort laser pulses without the necessity of optical isolators.

Noise characteristics of single-mode semiconductor lasers under external light injection

Presents a theoretical investigation of the noise behavior of a semiconductor laser operating under relatively strong light injection. Equations have been presented to describe the noise effect through the calculation of the relative intensity noise as well as the carrier-to-noise ratio available at the receiving end. Illustrative examples are given, showing the impact of the master and slave laser bias currents. Also, the injection-locked and free-running operation regimes have been comparatively analyzed. The results show how the noise characteristics are affected by optical injection and, consequently, how the operating conditions must be chosen to reduce this effect. In particular, it is shown, in agreement with previous works, that the master laser emission noise will essentially take the lead. As a result, to improve the noise behavior by injection locking a solitary laser, the use of a low-noise master laser is required. To make it easy to apply the present results to any laser diode under the stable-locking condition, the necessary relations are explicitly given before specifying the parameters of simulation.

Experimental observation of synchronization of chaos in erbium-doped fiber lasers

Synchronization of chaos has been observed in two erbium-doped fiber lasers. The spectrum study shows the slave laser shifts to the same wavelength of the master laser when the synchronization occurs.

Controlling chaos in a semiconductor laser by external optical injection

A theoretical analysis of the use of optical injection to control chaotic dynamics arising in an external cavity semiconductor laser has been undertaken. The work examines a master/slave laser configuration where chaos arising in the slave laser is shown to be replaced by periodic dynamics, and ultimately steady-state behaviour with increasing optical injection from the continuous wave master laser.

Theoretic and Experimental Study on Large－Frequency－Difference Side －Mode Injection Locking of High Power Semiconductor Lasers for Laser Cooling

The high power semiconductor lasers were side－mode injection locked with freque ncy difference 1300?GHz with respect to its free working frequency using inject ion locking technique.The transfer of coherent characteristic between the master laser and slave laser was studied experimentally in detail by using saturated a bsorption spectra and optical heterodyne technique.The relation of locking bandw idth versus the ratio of injection power and the mode building process of inject ion locking were measured and the experimental locking bandwidth agreed with the side－mode locking bandwidth obtained by multi－mode rate equation followed by injection term.The threshold injection light power for realizing side－mode inje ction locking was calculated theortically and tested by experiment.

High power broad-area diode laser at 794 nm injected by an external cavity laser

The output of a single-mode laser diode mounted in an external cavity has been injected in a 500 mW broad-area diode laser. A maximum of 120 mW single-mode emission at 794 nm has been obtained for an injected power of 2.6 mW. Almost 90% of the total output could be produced in a diffraction limited single spatial Gaussian lobe. The spectral properties of the master laser have been transferred to the slave to within 1.5 kHz. We present a study of the injection efficiency under variation of various physical and geometrical parameters while the master laser is held at a fixed frequency to within 10 MHz. In particular, in the course of variation of slave temperature and injection angle we observe strong resonance behaviour.

Message encoding and decoding using chaotic external-cavity diode lasers

Synchronization of chaotic external-cavity diode lasers has been studied in a master-slave configuration. A message is encoded into the chaotic master laser by amplitude modulation and transmitted to the slave laser. A scheme for decoding the message at the slave is demonstrated.

Recent Progress in Quantum Optics. Secure Communications Using Laser Chaos.

We have experimentally demonstrated synchronization of chaos generated in two Nd: YVO4 microchip lasers with master-slave coupling schemes. Synchronization was achieved when the optical frequencies of the master and the slave lasers are matched under injection locking. We conclude that the principle of chaos synchronization is regeneration of chaotic oscillations of the master laser in the slave laser cavitybecause the modulation parameters do not have to be matched between the two lasers.

Power-scalable system of phase-locked single-mode diode lasers

The direct use of diode lasers for high-power applications in material processing is limited to applications with relatively low beam quality and power density requirements. To achieve high beam quality one must use single-mode diode lasers, however with the drawback of relatively low optical output powers from these components. To realize a high-power system while conserving the high beam quality of the individual emitters requires coherent coupling of the emitters. Such a power-scalable system consisting of 19 slave lasers that are injection locked by one master laser has been built and investigated, with low-power diode lasers used for system demonstration. The optical power of the 19 injection-locked lasers is coupled into polarization-maintaining single-mode fibers and geometrically superimposed by a lens array and a focusing lens. The phase of each emitter is controlled by a simple electronic phase-control loop. The coherence of each slave laser is stabilized by computer control of the laser current and guarantees a stable degree of coherence of the whole system of 0.7. An enhancement factor of 13.2 in peak power density compared with that which was achievable with the incoherent superposition of the diode lasers was observed.

Reduction of Frequency Chirping in Semiconductor Lasers through Injection Locking

This paper analyzes the reduction of frequency chirp under injection locking of the modulated laser to the CW master laser. A closed-form analytical formula has been presented for chirp suppression. Light has been thrown upon the dependence of chirp reduction on the value of linewidth enhancement factor of the slave laser, master-slave detuning and the optical injection power. Effect of injection locking on the output AM index of the modulated laser has also been explored.

Data transparent reconfigurable optical interconnections using polarization switching in VCSEL's induced by optical injection

We demonstrate a data transparent reconfigurable optical interconnection system based on optical injection controlled polarization switching in a master-slave vertical-cavity surface-emitting laser (VCSEL) configuration. A 140-Mb/s data stream generated by the slave VCSEL is redirected by an anisotropic diffractive optical element depending on the polarization state of the emitted light. The polarization of the slave laser is controlled by injecting an orthogonally polarized optical signal from a master laser. The current modulation of the master VCSEL and the subsequent polarization switching of the slave VCSEL occur at 40 MHz. In our setup, both the data rate and the optical interconnection reconfiguration rate are limited by the electronic drive circuitry and could in principle attain the gigahertz range.

Injection locking of broad-area angled grating DFB lasers

The injection locking properties of an angled-grating distributed feedback laser have been measured experimentally. Fringe visibility measurements were used to ascertain the quality of the phase lock between the master and slave laser as a function of master coupling level and frequency detuning. Experimental results show an asymmetric lockband with the stable lock region increasing in width as the coupling is increased.

Narrow bandwidth operation of high-power broad-area diode laser using cascaded phase-conjugate injection locking

A broad-area laser is injection-locked by another broad-area laser that is also injection-locked by a single-mode diode laser. Two double-phase conjugate mirrors of photorefractive BaTaO3 are used to couple the master laser beams to the first slave laser, and the first slave laser output to the second slave laser. One of the double-phase conjugate mirrors is built up with the beams from two broad-area lasers. Two slave lasers are oscillating in single longitudinal mode at 808.5 nm and the spectral width is the same as that of the master laser. Final single-mode output power from the second slave broad-area laser is 840 mW, which is limited by the power of the injection beam. This work verifies the possibility of the multi-stage cascaded injection locking of high-power diode lasers with phase-conjugate injection.

Theory and experiment of a single-mode diode laser subject to external light injection from several lasers

A theoretical and experimental study of a graded-index separate confinement heterostructure (GRIN-SCH) distributed feedback (DFB) multiquantum-well (MQW) diode laser emitting at 1.55 /spl mu/m subject to external light injection from several lasers is presented. Lang's model for the classical single master-slave configuration is extended to include light injection from several master lasers. Free carrier transport effects are taken into account. An experimental validation of the model for two master lasers is made by means of a quantitative comparison between measured and calculated optical spectra. A fiber optics experimental setup makes it possible to measure precisely the power which is injected into the slave laser from each master laser. Measurements and model are in good quantitative agreement.

Encoded Gbit/s digital communications with synchronized chaotic semiconductor lasers

We numerically study the synchronization of two chaotic semiconductor lasers in a master-slave configuration. To synchronize the lasers, a small amount of output power from the master laser is injected, after propagating through an optical fiber, into the slave laser. We show that the output of the master laser can be used as a chaotic carrier to encode a digital message which can be recovered after propagating long distances. We also check the robustness of this scheme when the two lasers are slightly different.

Novel measurement scheme for injection-locking experiments

A novel experimental setup for injection-locking experiments is presented. The single-mode-fiber-based configuration allows one to precisely control the power and the polarization state of the light injected from the master laser into the slave laser cavity. Different behaviors typical for injection locking with single-mode semiconductor lasers (e.g., stable injection locking, undamped relaxation oscillations, nearly degenerate four-wave mixing, period doubling, chaotic behavior) are experimentally observed and theoretically verified using a rate-equation-based model. Measurements and calculations are entirely linked analytically and thoroughly compared by means of the corresponding power spectra. The good quantitative agreement between measurements and model validates the model, the analytical approach, and the experimental setup.

Extreme timing jitter reduction of a passively mode-locked laser diode by optical pulse injection

Reduction of the timing jitter to less than that of the master laser pulses was achieved for a passively mode-locked laser diode stabilized by subharmonic-frequency optical pulse injection. Detailed investigation revealed that this phenomenon originates from the short-term stability of the mode locking frequency under passively mode-locking operation with suitable bias conditions of the saturable absorber and the gain sections.

High-Power and Highly-Stable Solid-State Laser for the Gravitational Wave Detector.

A high-power and highly-frequency-stabilized laser has been developed for the laser interferometric gravitational wave detector. Requirements of the light source for this are a single transverseand longitudinal mode with the power and frequency noise of 10W and 10-6Hz√Hz at 300 Hz, respectively. The frequency of a LD-pumped injection-locked Nd: YAG laser was stabilized to a high finesse Fabry-Perot optical resonator that was isolated from seismic and acoustic noise, which was achieved by controlling master laser light. We evaluated the mechanical and thermal stability of Fabry-Perot cavities of both rigid spacer type and the independently suspended mirrors type. Finally we have achieved the absolute frequency noise of2×10-2Hz/√ Hz for an injection-locked high-power laser with the output power of 9.8 W.

A sideband-injection locked extended cavity diode laser for interrogating cold trapped Strontium ions

A simple optical sideband injection locking technique is demonstrated to frequency offset-lock a 674 nm slave extended cavity diode laser to a single frequency source. By injecting light from a master laser into either sideband of the frequency modulated extended cavity slave laser, it is shown that the carrier of the slave is frequency locked to the master laser with a relative linewidth much less than 10 Hz. The locking bandwidth is investigated to determine the largest capture range. An observation of the 674 nm 2 S 1/2– 2 D 5/2 transition in a single ion of 88 Sr + was performed using this laser system, yielding ≈1 kHz linewidth Zeeman structure, limited by the master laser linewidth. National Physical Laboratory

Observation of optical bistability in a GaAlAs semiconductor laser under intermodal injection locking

Experimental observation of optical bistability in a semiconductor laser under intermodal injection locking is reported for what is believed to be the first time. It is seen that a change in injection power of several microwatts or master laser frequency detuning of a few hundred megahertz can induce a change of as much as several hundred gigahertz in the lasing frequency of the slave laser. The results are in qualitative agreement with theoretical predictions.