Injection locking of a diode laser locked to a Zeeman frequency stabilized laser oscillator

We describe the design and performance of an injection-locked diode laser locked to a stabilized, single frequency, unmodulated diode laser. The master oscillator is a grating-tuned, external cavity diode laser which is stabilized on a Doppler free alkali metal resonance transition frequency via Zeeman locking. The master oscillator frequency is shifted by an acousto-optic modulator, which provides optical isolation of the master oscillator laser while tuning of the acousto-optic modulation frequency can also provide frequency offset tuning. The slave laser is a free running diode which is injection-locked by a small fraction of the frequency shifted master oscillator light. Good long- and short-time frequency stability are observed for both the Zeeman-locked master oscillator and the injection-locked slave laser.     

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. Received: 18 November 1998 / Revised version: 29 January 1999 / Published online: 7 April 1999     

Intensity and frequency noise characteristics of two coherently-added injection-locked Nd:YAG lasers

Coherent addition of two injection-locked Nd:YAG lasers has been performed. A maximum output power of 4.4 W and addition efficiency of 0.94 was achieved, which is the highest power-coupling efficiency ever reported. It was shown experimentally that the frequency and intensity noise level of the coherently-added laser are the same as those of a single injection-locked laser. In particular, no additional intensity noise was observed above the relaxation oscillation frequency of the slave laser, which is suitable for use as the light source for a future gravitational wave detector. The frequency noise of the coherently-added laser was suppressed to 1×10^-4 Hz/ by controlling that of the master laser, and the intensity noise was also suppressed to 1×10^-8 / by controlling the intensity of pump lasers used for the slave lasers. Received: 11 April 2001 / Revised version: 20 June 2001 / Published online: 19 September 2001     

Synchronous Injection Locking Operation of Monolithic Diode Lasers Mode-Locked Diode Lasers

Synchronized mode-locking of monolithic mode-locked diode lasers has been demonstrated by injecting the light output from a master monolithic mode-locked diode laser. The master diode laser is a 10 GHZ hybridly mode-locked two section InGaASP quantum well laser. The slave lasers are a 10 GHz two section laser which is similar to the master laser, and a 20 GHz three section colliding pulse mode-locking laser. Both the slave lasers were greatly stabilized at 10 GHz frequency by a synchronous mode-locking mechanism under the injection of master laser pulses.     

Investigation on amplitude and frequency noise of injection-locked diode-pumped Nd:YAG lasers

Amplitude and frequency stability of an injection-locked diode-pumped miniature Nd:YAG ring laser were measured. The mechanism of amplitude-noise transfer to the injection-locked slave laser was experimentally investigated and consequences for the injection locking of solid-state lasers operating at high output powers are discussed.     

Amplitude-squeezed, frequency-modulated, tunable, diode-laser-based source for sub-shot-noise FM spectroscopy

We have developed a frequency-modulated, tunable, amplitude-squeezed, diode-laser-based source and used it to perform FM spectroscopy on rubidium. The setup consists of a free-running diode laser injection locked by a frequency-stabilized, current-modulated diode laser. The injection-locked slave laser beam adopted the frequency spectrum of the master laser beam while rejecting residual AM in the master laser beam by more than 50 dB. Injection locking also enhanced amplitude squeezing in the slave laser beam by suppressing uncorrelated longitudinal sidemodes. The noise floor of the measurement was 0.8 dB below the shot-noise level.     

强光注入提高光反馈VCSELs混沌载波基频

研究了外部光注入对光反馈垂直腔表面发射半导体激光器(VCSEL)混沌载波基频的影响.研究结果表明：当外部注入光频率与VCSEL自由运行的振荡频率失谐一定时,随着外部光注入强度的增加,混沌载波基频总体呈现上升的趋势;通过调整失谐频率和注入强度大小,外部光注入可以使混沌载波基频得到大幅度的提高;当归一化的注入系数K=330, 失谐频率为42 GHz,可得到基频位于47.3 GHz的混沌信号输出. 关键词： VCSEL 光注入 光反馈 混沌载波基频     

Sweep optical frequency synthesizer with a distributed-Bragg-reflector laser injection locked by a single component of an optical frequency comb

A sweep optical frequency synthesizer is demonstrated by using a frequency-stabilized optical frequency comb and injection-locked distributed-Bragg-reflector (DBR) laser diode. The injection-locked DBR laser acts as a single-frequency filter and, simultaneously, a high-gain amplifier of the optical frequency comb. The frequency instability of the heterodyne beat signal between two independently injection-locked DBR lasers is measured to be 2.3 x 10(-16) at 1 s averaging time. The output frequency of the sweep optical frequency synthesizer can be precisely tuned over 1 GHz, and a saturated absorption spectrum of the Cs D2 line at 852 nm is recorded by the injected DBR laser.     

Generation of phase-coherent laser beams for Raman spectroscopy and cooling by direct current modulation of a diode laser

A setup for generation of GHz side-bands by direct current modulation of a diode laser is described. The first order side-bands are used to inject two slave power diode lasers, in order to produce phase coherent, controllable frequency shifted, light beams, the mutual phase coherence of which has been verified (beat-note FWHM of 1 Hz, instrumentally limited). Some possible applications in the context of laser Raman cooling of cesium atoms are briefly discussed. Received 9 November 1998 and Received in final form 16 February 1999     

Anticipation in the synchronization of chaotic semiconductor lasers with optical feedback

The synchronization of chaotic semiconductor lasers with optical feedback is studied numerically in a one-way coupling configuration, in which a small amount of the intensity of one laser (master laser) is injected coherently into the other (slave laser). A regime of anticipated synchronization is found, in which the intensity of the slave laser is synchronized to the future chaotic intensity of the master laser. Anticipation is robust to small noise and parameter mismatches, but in this case the synchronization is not complete. It is also shown that anticipated synchronization occurs in coupled time-delay systems, when the coupling has a delay that is less than the delay of the systems.     

Switching time in optically bistable injection-locked semiconductor lasers

Switching between states in a dispersive bistable injection-locked slave laser has been theoretically investigated. We show that the switching can be achieved by relatively small and short (≈10-50?ps) variation of the master laser injection power or frequency, which, besides the variation of the slave laser optical power, leads to significant variation of its photon phase (≈5π/6). By using an analytical model, we calculate the switching time dependence on the magnitude of the injection power and the frequency detuning variation.     

Diode laser frequency stabilisation for water-vapour differential absorption sensing

We describe a low-power continuous-wave laser system for water-vapour sensing applications in the 935-nm region. The system is based on extended-cavity diode lasers and distributed-feedback lasers and delivers four single-mode frequency-stabilised optical signals. Three lasers are locked to three water-vapour absorption lines of different strengths, whereas the fourth lies outside any absorption line. On-line stabilisation is performed by wavelength-modulation spectroscopy using compact water-vapour reference cells. An offset-locking technique implemented around an electrical filter is applied for the stabilisation of the off-line slave laser to an on-line master laser at a frequency detuning of 18.8 GHz. Stabilities in the order of 15 MHz over one day were observed for the strongest lines, at the detection limit of the measurement instrumentation. The developed techniques and schemes can be applied to other wavelength ranges and molecular species. Differential absorption lidar instrumentation can in particular benefit from such a system when the stabilised lasers serve as injection seeders to pulsed power oscillators. PACS 42.62.Fi; 42.72.-g; 42.68.Wt     

Realization of Optical Phase Locked Loop at 9.2GHz between Two Independent Diode Lasers

The optical-phase-locked-loop (OPLL) at 9.2GHz between two independent narrow linewidth diode lasers is realized. Ultrabroad servo bandwidth at 4MHz is first achieved and it is guaranteed that the full spectral characteristics of the master laser can be transferred to the slave laser. The experimental results prove that the coherence between two lasers is about 99%. This offers a new method to study the interaction between lasers and atoms based on the ground hyperfine structure of caesium atoms.     

Femtosecond noncollinear and collinear parametric generation and amplification in BBO crystal

Measurements of intensity and frequency noise of an injection-locked 5-W Nd:YAG laser are presented and compared with the predictions of models. We show that the output of the injection-locked laser has very low levels of noise, and that the measurements support the predictions of the models. Thus these models can confidently be used to predict the performance of high-power, injection-locked lasers being developed for gravity wave detection. Received: 31 January 2000 / Revised version: 18 March 2000 / Published online: 16 June 2000     

Optical spectral relation between the master and the frequency-locked slave lasers

In this paper, the spectral relation between the master and the frequency-locked slave laser (FLSL) is investigated by the conventional technique of optical intensity modulation and optical heterodyne. Experimentally, we demonstrate that under complete and stable locking condition, the lightwave of the FLSL and the sidebands of the master laser produced by the optical intensity modulation are perfectly coherent (frequency coherence). Referring to our recent studies, the lightwave of the master laser and its corresponding sidebands are also perfectly coherent. Additionally, the spectral structures of two perfectly coherent lightwaves are identical in the level of wave train. Therefore, we indirectly verify that the spectral structures of the FLSL and the master laser are identical in the level of wave train.     

Correlation dimension signature of wideband chaos synchronization of semiconductor lasers

Chaos data analysis has been performed on the chaotic output power time series data from a synchronized transmitter-receiver pair of semiconductor lasers. The system uses an asymmetric, bidirectional coupling configuration between the master (transmitter), which is a laser diode with optical feedback, and a stand-alone slave semiconductor laser. The correlation dimension of the chaotic time series has a minimum value of 4, which was obtained from high-bandwidth measurements. The correlation dimensions for both the master and the synchronized slave are identical when the cross-correlation coefficient of the synchronized chaos is above 0.9. These results establish correlation dimension analysis as an effective tool for the determination of the quality of wideband chaos synchronization.     

Accurate frequency control of a mode-locked laser diode by reference-light injection

Injection locking is employed to narrow the spectrum linewidth of individual modes of an active mode-locked laser diode (ML-LD). The multiple modes of the injection-locked ML-LD lie over 3.0 THz with 25-GHz spacing at 30 dB down; their linewidth and stability, ~25 MHz, are nearly the same as those of the master laser. We also demonstrate the accurate frequency measurement of laser diodes stabilized to molecular (H(13)C (15)N ,(13)C(2)H (2)) absorption lines by use of the injection-locked ML-LD.     

Comparison of two types of synchronization of external-cavity semiconductor lasers

We study numerically the synchronization of external-cavity semiconductor lasers in a master-slave configuration, based on a Lang-Kobayashi-type model. Depending on the feedback and coupling strengths, the slave laser synchronizes with the injected optical field or with the injected field but lags in time. We show that these two types of synchronization present different robustness with respect to the noise, frequency detuning, and current modulation of the master laser.     

40K-87Rb原子冷却的半导体激光系统

对⁴⁰K-⁸⁷Rb原子冷却的半导体激光系统提出了一种实验方案，并进行了初步实验.采用三台外腔光栅反馈半导体激光器(ECDL)、四台注入锁定从激光器和一台半导体激光放大器组成激光系统.三台ECDL通过声光调制器产生四束光，分别作为⁴⁰K和⁸⁷Rb原子的冷却光和再抽运光，四束不同频率成分的激光分别注入锁定四台从激光器，然后Rb 冷却光、K冷却光和K再抽运光再同时注入半导体激光放大器进行放大.该装置可同时产生冷却⁴⁰K和⁸⁷Rb原子的冷却光和再抽运光，结构紧凑、工作稳定. 关键词： 简并费米气体 激光器系统 外腔光栅反馈半导体激光器 半导体激光放大器     

Slave-master dynamics of semiconductor laser with short external cavity

In this paper, the dynamical response of a slave semiconductor laser, with short cavity, under injection of a chaotic light from a master semiconductor laser has been widely studied. This is analyzed numerically via bifurcation diagrams, in terms of the phase and strength of the feedback, as control parameters. It is shown that, both of these parameters should be considered in the dynamical response of the slave laser. Our numerical calculations show that the dynamics of the slave laser imitates the master laser, in addition to the feedback strength, it also heavily depends on the injection dynamics and rates. Numerical results also show that for different values of the control parameters, the intensity of the slave laser output can be fully different from the injection source. However, we found out under appropriate conditions, that the dynamics of the slave can be the same as the master laser. The results also show that the output of the slave laser, compared to its output without injection, can be stabled in the appropriate values of the injection rate from the master laser.