Master Laser Research Articles

Integrated Two-Section Discrete Mode Laser

The authors present the design and characterization of a novel integrated two-section discrete mode index patterned diode laser source. The two slotted regions etched into the laser ridge waveguide are formed in the same fabrication step as the ridge, thus avoiding the requirement for complex lithography and regrowth steps. The laser is encased in a temperature-controlled butterfly package, which simplifies the static and dynamic measurements. Initial static characterization of this two-section laser shows that the injection, from the master laser to the slave laser, enhances the slave's emission side-mode suppression ratio from 30 dB to over 50 dB and its relative intensity noise is reduced from about -129.3 dB/Hz to -142.6 dB/Hz. Subsequent dynamic characterization then shows that the modulation bandwidth of the laser can be improved via injection to about three times the inherent free-running bandwidth. Hence, optical injection from master section into slave section enables the improvement of various parameters, which makes this two-section device attractive as a transmitter in optical communication systems.

Dual-beam optically injected semiconductor laser for radio-over-fiber downlink transmission with tunable microwave subcarrier frequency

We propose a downlink broadcast transmission scheme of radio-over-fiber (RoF) system based on period-one (P1) dynamic of dual-beam optically injected semiconductor laser with tunable microwave subcarrier frequency. The transmission performance of 2.5Gb/s data in a 60GHz RoF system is demonstrated through numerical simulations. It is found that the proposed transmission scheme can easily generate a single-sideband (SSB) optical modulation by adjusting the injection strength level of two master lasers (ML), which is favorable to reduce the fading effect due to chromatic dispersion. Furthermore, influences of the pulse amplitudes and duty cycles of the downlink data on the transmission properties are investigated. It is observed that the oscillation of the relative power at the base station induced by fiber dispersion does not vary apparently with the modulation parameters. Once the SSB spectrum is generated by dual-beam optical injection, the downlink transmission performance of the proposed RoF system keeps good stability and reliability.

Photonic generation of high-frequency microwave signals utilizing a multi-transverse-mode vertical-cavity surface-emitting laser subject to two-frequency orthogonaloptical injection

We study photonic microwave signal generation obtained when single- and multi-transverse-mode vertical-cavity surface-emitting lasers (VCSELs) are subject to two-frequency orthogonal optical injection. Our calculations show that broadly tunable microwave signals can be obtained in these systems. The response of the multi-transverse-mode VCSEL is enhanced with respect to that obtained with a similar single-transverse-mode VCSEL subject to the same two-frequency orthogonal optical injection. The extra degree of freedom given by the multi-transverse-mode operation of the VCSEL under two-frequency orthogonal optical injection enhances the performance of the photonic microwave generation system, because the higher-order transverse mode is excited with a much larger amplitude than that of the fundamental transverse mode. Periodic oscillations are obtained for a very wide range of frequency detunings between the optical injections and transverse modes. A relative maximum of the microwave signal amplitude is obtained when the frequency of one of the optical injections is very close to the frequency of the orthogonally polarized fundamental mode of the VCSEL. Periodic oscillations are demonstrated for symmetric and asymmetric values of the injection strengths. Wide tuning ranges, extended into the THz band, are obtained in our system. Our results show that the proposed microwave signal generation mechanism is independent of the polarization of the master lasers.

Multiuser optical communication system based on generalized and complete synchronization

In this paper, we numerically explore the potential of multiuser optical communication system based on generalized and complete synchronization. The two mutually delayed coupled master lasers in the transmitter and receiver sides are completely synchronized to provide the identical driving signal. Different slave lasers are coupled to the driving signal in a master-slave configuration and thus display generalized synchronization between the master laser and slave lasers in both sides, while the corresponding slave lasers in the transmitter and receiver are completely synchronized due to the identical driving signal and their identical device parameters. We show the capacity of the proposed system for encoded message transmission in a multiuser chaos-based communication scenario.

Photonic Generation of Wideband Time-Delay-Signature-Eliminated Chaotic Signals Utilizing an Optically Injected Semiconductor Laser

Photonic generation of wideband chaotic signals with time delay signature elimination is investigated experimentally and numerically based on a semiconductor laser (slave laser) with chaotic optical injection from a master laser. The master laser is subject to moderate optical feedback where the feedback strength and external-cavity length are fixed, while the slave laser stands alone. The experimental results show that wideband chaotic signals with successful time delay concealment can be generated in the slave laser by simply adjusting the coupling strength and frequency detuning between the two lasers. Furthermore, the numerical results are in accordance with the experimental observations. Finally, we propose a simple method for simultaneously generating multiple streams of high-quality chaotic signals using multichaotic lasers, where the time delay is effectively concealed in the autocorrelation function and delayed mutual information calculated from the chaotic time series.

Generation and Modulation of a Millimeter-Wave Subcarrier on an Optical Frequency Generated via Optical Injection

A highly tunable millimeter-wave subcarrier signal is generated by optically injecting a Fabry-Perot semiconductor laser. The optically injected light, which enables microwave subcarrier frequencies well beyond the injected laser's free-running relaxation-oscillation frequency, is then on-off keyed by direct-current (dc) modulation of the injected slave laser. Adjustment of the subcarrier frequency is easily accomplished by changing either the dc bias current and/or junction temperature of the injected slave or the injecting master laser. In this paper, we theoretically and experimentally investigate the purity of the modulated microwave subcarrier. The generated microwave signal was then transmitted over 50 km of single-mode fiber, demonstrating the applicability of a directly modulated slave laser optically injected into the period-one state for radio-over-fiber applications.

Randomness-Enhanced Chaotic Source With Dual-Path Injection From a Single Master Laser

The randomness and bandwidth enhancement of chaotic signals in optically injected semiconductor lasers (SLs) with dual-path injection from a single master laser are investigated experimentally and numerically. It is shown that both the randomness and bandwidth of chaotic signals generated in a slave SL (SSL) can be enhanced significantly, especially for positive frequency detuning, by simply adding an additional injection path in the conventional master-slave configuration. The region of injection parameter space leading to wideband randomness-enhanced chaos in SSL can be greatly broadened compared to the SSL with single-path injection. This low-cost and simple configuration for wideband randomness-enhanced chaotic source is highly desirable for high-speed random number generators based on chaotic SLs.

Optical and RF stability transfer in a monolithic coupled-cavity colliding pulse mode-locked quantum dot laser

We report a novel quantum dot based laser design where a stable high-Q master laser is used to injection lock a passively mode-locked monolithic colliding pulse slave laser. Coupling between the crossed orthogonal laser cavities is achieved through a common monolithically integrated saturable absorber, which results in the locking and hence reduction of the timing jitter as well as the long-term frequency drift of the slave laser. A stable 30 GHz optical pulse train is generated with more than 10 dB reduction in the RF noise level at 20 MHz offset and close to 3 times reduction in the 10 dB average optical linewidth of the slave laser.

Providing $10^{-16}$ Short-Term Stability of a 1.5-$\mu\hbox{m}$ Laser to Optical Clocks

We report on transferring 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-16</sup> -level fractional frequency stability of a “master laser” operated at 1.5 μm to a “slave laser” operated at 698 nm, using a femtosecond fiber comb as transfer oscillator. With the 698-nm laser, the <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> - <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> clock transition of <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">87</sup> Sr was resolved with a Fourier-limited linewidth of 1.5 Hz (before: 10 Hz). Potential noise sources contributed by the frequency comb are discussed in detail.

Efficient pulse amplification using a transverse-flow CO_2 laser for extreme ultraviolet light source

We constructed a master oscillator power amplifier CO2 laser system using a transverse-flow, RF-pumped CW CO2 laser. We carried out an amplification test at a 100% duty cycle of pumping discharge with the electrical input for the discharge up to 60 kW. An output power of 1.90 kW was achieved at the oscillator repetition rate of 100 kHz and the optical input power of 13 W. The electrical-to-optical efficiency was 3.1%.

Wideband Unpredictability-Enhanced Chaotic Semiconductor Lasers With Dual-Chaotic Optical Injections

The unpredictability degree and bandwidth properties of chaotic signals generated by semiconductor lasers subject to dual chaotic optical injections (DCOI) are investigated numerically. The unpredictability degree is evaluated quantitatively via permutation entropy. Compared with the slave laser (SL) subject to single chaotic optical injection, both the chaotic bandwidth and the unpredictability degree can be enhanced significantly for SL with DCOI. The effects of injection strength, frequency detuning as well as feedback strength are considered. It is shown that, with the increase of injection strength, the unpredictability degree of chaotic signals generated by SL increases firstly and then decreases until saturates at a constant level. Positive frequency detuning is preferred to achieve wideband unpredictability-enhanced chaos, and higher bandwidth and unpredictability degree can be further expected by adopting two differently detuned master lasers. The physical mechanisms behind the wideband unpredictability-enhanced chaos are also revealed. The wideband unpredictability-enhanced chaotic signals generated by SL with DCOI are extremely useful for high speed random number generators, as well as for high capacity security-enhanced chaotic communications.

Controllable Dual-Wavelength Fiber Laser

We demonstrate a controllable dual-wavelength fiber laser which contains a master laser and a slave laser. The master laser is a kind of ring cavity laser which can be injected into by the slave laser. The output laser wavelength is controlled by injected power of the slave laser; both single- and dual-wavelength operation can be achieved. Under free running, the master laser generates 1064 nm laser output. Here the slave laser is a 1072 nm fiber laser. The 1064 nm and 1072 nm laser coexist in output spectrum for relatively low injected power. Dual-wavelength and power-ratio-tunable operation can be achieved. If the injected power of the slave laser is high enough, the 1064 nm laser is extinguished automatically and there is only 1072 nm laser output.

Precision and fast wavelength tuning of a dynamically phase-locked widely-tunable laser

We report a precision and fast wavelength tuning technique demonstrated for a digital-supermode distributed Bragg reflector laser. The laser was dynamically offset-locked to a frequency-stabilized master laser using an optical phase-locked loop, enabling precision fast tuning to and from any frequencies within a ~40-GHz tuning range. The offset frequency noise was suppressed to the statically offset-locked level in less than ~40 μs upon each frequency switch, allowing the laser to retain the absolute frequency stability of the master laser. This technique satisfies stringent requirements for gas sensing lidars and enables other applications that require such well-controlled precision fast tuning.

Heterodyne interferometer laser source with a pair of two phase locked loop coupled He–Ne lasers by 632.8 nm

Two He–Ne lasers are frequency and phase coupled by phase locking loop technique for a heterodyne laser interferometer. The heterodyne He–Ne laser is built of stabilized commercially used laser tubes. The two lasers create a high frequency stable heterodyne laser source with an output power of 2 mW. The laser source is coupled by two fibers (one fiber per laser) to the heterodyne laser head. This paper describes the configuration and the control theory basics of the laser system. The experimental setup and the equipment used are also described. First, experimental results with different parameters are represented. Then we discuss a novel heterodyne laser source which has achieved a master laser frequency stability of Δf1/f1 = 1 · 10−8 and a beat frequency stability of approximately Δfbeat/fbeat ≈ 4.5 · 10−5.

Precision laser development for interferometric space missions NGO, SGO, and GRACE Follow-On

Optical fiber and semiconductor laser technologies have evolved dramatically over the last decade due to the increased demands from optical communications. We are developing a laser (master oscillator) and optical amplifier based on those technologies for interferometric space missions, including the gravitational-wave missions NGO/SGO (formerly LISA) and the climate monitoring mission GRACE Follow-On, by fully utilizing the matured wave-guided optics technologies. In space, where simpler and more reliable system is preferred, the wave-guided components are advantageous over bulk, crystal-based, free-space laser, such as NPRO (Non-planar Ring Oscillator) and bulk-crystal amplifier.

Modulation response and bandwidth of injection-locked Fabry–Pérot laser diodes

In this paper, we investigate the modulation response and the −3 dB bandwidth of a side-mode injection-locked Fabry–Pérot semiconductor laser. In the study, we use small-signal analysis, based on a set of linearized multimode rate equations extended by terms taking into account the power and the detuning frequency of injected light from the master laser. Our analysis shows that for the optimum injection power and detuning, the bandwidth of side modes in the vicinity of the gain maximum may be twice as large as that in the free-running regime.

BANDWIDTH ENHANCEMENT IN CHAOTIC SEMICONDUCTOR LASERS WITH STRONG CHAOTIC OPTICAL INJECTION

The bandwidth properties of chaotic signals generated by semiconductor lasers subject to strong chaotic optical injection (COI) are investigated numerically. The chaotic output of an injection master laser (ML) is injected into the slave laser (SL). The effects of feedback strength, injection strength and bias current on the bandwidth properties are discussed in detail. Some novel results are found, the bandwidth for SL increases with the injection strength firstly until reaches a maximum, and then decrease to approach the bandwidth of ML due to the injection-locking chaos synchronization. Large feedback strength and bias current contributes to higher maximum chaotic bandwidth in the range of injection strength. That is to say, for given parameters, optimal injection strength exists contributing to highest chaotic bandwidth, and moves to a large value for a large feedback strength and bias current, which is extremely useful for increasing the transmission rate of the optical chaotic communication system.

Stability of the nonlinear dynamics of an optically injected VCSEL

Automated protocols have been developed to characterize time series data in terms of stability. These techniques are applied to the output power time series of an optically injected vertical cavity surface emitting laser (VCSEL) subject to varying injection strength and optical frequency detuning between master and slave lasers. Dynamic maps, generated from high resolution, computer controlled experiments, identify regions of dynamic instability in the parameter space.

Alternative laser system for cesium magneto-optical trap via optical injection locking to sideband of a 9-GHz current-modulated diode laser

By optical injection of an 852-nm extended-cavity diode laser (master laser) to lock the + 1-order sideband of a ~9-GHz-current-modulated diode laser (slave laser), we generate a pair of phase-locked lasers with a frequency difference up to ~9-GHz for a cesium (Cs) magneto-optical trap (MOT) with convenient tuning capability. For a cesium MOT, the master laser acts as repumping laser, locked to the Cs 6S₁/₂ (F = 3) - 6P₃/₂ (F' = 4) transition. When the + 1-order sideband of the 8.9536-GHz-current-modulated slave laser is optically injection-locked, the carrier operates on the Cs 6S₁/₂ (F = 4) - 6P₃/₂ (F' = 5) cooling cycle transition with -12 MHz detuning and acts as cooling/trapping laser. When carrying a 9.1926-GHz modulation signal, this phase-locked laser system can be applied in the fields of coherent population trapping and coherent manipulation of Cs atomic ground states.

Phase-coherent repetition rate multiplication of a mode-locked laser from 40 MHz to 1 GHz by injection locking

We have used injection locking to multiply the repetition rate of a passively mode-locked femtosecond fiber laser from 40 MHz to 1 GHz while preserving optical phase coherence between the master laser and the slave output. The system is implemented almost completely in fiber and incorporates gain and passive saturable absorption. The slave repetition rate is set to a rational harmonic of the master repetition rate, inducing pulse formation at the least common multiple of the master and slave repetition rates.