Slave Laser Research Articles

Dual‐channel, high‐frequency optoelectronic oscillators utilizing optically‐injected lasers

AbstractWe propose a novel approach to dual‐channel optoelectronic oscillators (OEOs) with enhanced frequency band by leveraging directly modulated (DM) semiconductor lasers under optical injection. In this configuration, the frequency‐tuned optical signal from a master laser is introduced into a single‐mode slave laser, facilitating multioptical‐mode operation. The resulting multiple optical frequencies emitted by the slave laser facilitates a DM‐OEO signal at a frequency exceeding the laser's intrinsic modulation bandwidth. Through the deployment of a dual‐channel OEO based on the DM multimode laser signal, stable oscillation signals have been successfully achieved simultaneously at 15 and 18 GHz with phase noise levels of 96.43 and 95.62 dBc/Hz, respectively, at a 10‐kHz offset frequency.

Frequency pushing and pulling in semiconductor lasers subject to optical frequency comb injection

We theoretically investigate the frequency shift of a free-running semiconductor laser when optically injected by an optical frequency comb. By numerical integration of the laser rate equations, we have identified two types of frequency shifts, frequency pulling, and frequency pushing. The free-running slave laser seems to switch between pulling and pushing in a regular manner. We have systematically determined the dependence of these shifts on comb parameters, including comb spacing and number of lines. We have found that the occurring frequency pushing seems to be almost independent of comb signals and comb spacing, while in contrast, the frequency pulling shows weak dependence on comb signals but largely affected by comb spacing. We have also shown that carrier density dynamic is the origine of these phenomena.

Simplified coherent chaotic optical secure communication scheme based on the Kramers-Kronig receiver.

Enhancing physical layer encryption in fiber-optic networks remains a challenging yet vital task. In this Letter, we propose a simplified coherent chaotic secure optical communication scheme based on the Kramers-Kronig (KK) receiver. This scheme incorporates a semiconductor laser with a phase-conjugated optical feedback serving as a common chaotic source, and its chaotic output is directly injected into the two slave lasers arranged separately at the transmitter and receiver end to achieve high-quality synchronization of chaotic signals, with a corresponding chaotic bandwidth of 30.6 GHz. By virtue of the common-signal-induced broad chaotic synchronization, a proof-of-principle demonstration is successfully conducted. It involves the secure transmission of a 20 Gbaud 16-level quadrature amplitude modulation (16QAM) signal over a 50 km standard single-mode fiber (SSMF) link. At the receiver end, we deploy a KK receiver to reconstruct the field of the optical signal and hence enable signal compensation and recovery with offline digital signal processing (DSP). This method simplifies device requirements in the current chaotic coherent optical secure communication, offering a cost-effective mode and promising path for advancing physical layer encryption in inter-data center communications.

Random Numbers Generated Based on Dual-Channel Chaotic Light

This paper presents a chaotic system based on novel semiconductor nanolasers (NLs), systematically analyzing its chaotic region and investigating the influence of key parameters on the unpredictability of chaotic output. This study found that under optical feedback conditions, NLs generate chaos across a wide range of feedback parameters, with the highly unpredictable region completely overlapping with the chaotic region. Further injection into the slave lasers enhances the chaotic output, expanding the range of unpredictability. Additionally, we analyzed the impact of internal parameter mismatch on the complexity of chaotic signals and found it to be similar to the scenario when parameters are matched. Using this chaotic system as an entropy source, we constructed a random number generator (RNG) and investigated the effects of internal parameters mismatch and differences in the injection parameters on the generator’s performance. The simulation results show that the RNG performs well under different parameter settings, and the generated random sequences pass all random number tests successfully. Therefore, this chaotic system can yield a high-complexity chaotic light source with appropriate parameter selection, and when combined with effective post-processing, it can generate high-quality random numbers. This is crucial for advancing the realization of small-sized, high-randomness RNGs.

Multiplexed FBG-FFPI strainmeter array for field observation

Mining mass data of the earth's surface deformation is a promising approach for earthquake early-warning, raising an urgent demand for developing large-scale optical fiber strainmeters. This paper presents the implementation and results of large-scale, ultrahigh-resolution, real-time multiplexed fiber Bragg grating-based Fabry-Perot interferometer (FBG-FFPI) strainmeter arrays for field observation. The Pound-Drever-Hall technique locks master and slave single-sideband lasers onto the FBG-FFPI resonance peaks for precise strain measurement. A 10-channel array was successfully utilized for field observation at Lijiang National Seismic Station, which accurately recorded over 100 earthquakes and the earth's daily tide signal. The FBG-FFPIs have a strain resolution of 4.80 pε/√Hz @ 30 Hz with a 0.22-m cavity length. A 4-channel array with a longer cavity length of 1.4 m was also established at Heqing Seismic Station, showing advantageous performances. These results demonstrate the significant potential of FBG-FFPI strainmeter arrays in providing geophysical data for earthquake early-warning and hazard mitigation.

Optically injected quantum dot lasers and its complex dynamics

Abstract Lasers are paradigmatic examples of nonlinear systems and have played a crucial role in developing nonlinear dynamics into an interdisciplinary topic. Indeed, a freely operating laser represents a nontrivial system, but the phenomena that occur are much more interesting when the laser is exposed to external factors such as optical feedback (OFB) and optical injection (OI). This paper deals with the analysis of the dynamic behavior of a quantum dot semiconductor laser (QDSL) model under the influence of optical injection from another laser. The proposed model was studied numerically with the help of MATLAB. A QDSL system with optical injection was proposed and studied numerically. The quantum dot (QD) laser was used, which is a quantum semiconductor laser and has strong stability without external perturbation. When it is subjected to feedback, it has a critical effect on the follower laser and changes its stable behavior before injection to a set of nonlinear dynamics. The effect of both optical feedback strength and the delay time on the performance and behavior of the bifurcation patterns in the follower laser output was studied, taking into account changing the bifurcation parameters, the injection force k, the slave laser frequency, and the slave laser delay time. The behavior of the slave was studied each time and compared with the behavior of the master. We observed the chaotic paths (essentially stable and continuous pulsating oscillations evolving into periodic and semi-periodic oscillations and then chaotic ones). The time series corresponding to the bifurcation diagrams and the probability of the time interval between spikes and attractors were studied.

Transponder-type laser interferometer prototype for spaceborne gravitational wave detectors.

Transponder-type laser interferometry is essential in spaceborne gravitational wave detection missions. This paper presents a transponder-type laser interferometer prototype for potential noise calibration of spaceborne gravitational wave detectors. Using a digital optical phase-locked loop, we successfully locked the phase of the slave laser to the master laser (∼200p W). Once the link between the master laser and the slave laser is established, the two satellites (essentially two lasers) form a transponder-type laser interferometer. We carefully analyze the measurement stability and noise characteristics of the interferometer, and the results show that the Allan deviation of the zero drift can reach 243.2pm at t=0.429s, while the noise spectral density has a typical 1/f line shape with a floor of 21p m/H z 1/2 at 1Hz. The coherence analysis shows that the temperature drift is an important factor limiting the performance of the interferometer below 2mHz, while the frequency noise of the master laser is not dominant in the experiment. Transponder-type laser interferometers have a wide range of applications in intersatellite communication and measurement. Our design can serve as a valuable reference for gravitational wave detection missions such as LISA.

Phase-locked, pre-amplified optical injection locking at low input powers.

Optical injection locking generally occurs when light from a master laser is unidirectionally injected into a slave laser, such that the injected light overcomes spontaneous emission inside the cavity, and forces the slave laser to behave as a frequency copy of the master. Here, we study the limits of stability for optically pre-amplified optical injection locking in the case of large added noise on the input field and in the presence of a phase locked loop which minimizes the frequency offset between master and slave lasers. We present a set of modified rate equations which we use to describe the physics of the system near the limit of stable injection locking, and report on phase slips which occur due to injected noise momentarily destabilizing the system. We then provide experimental evidence to support the behavior seen in simulation, and are able to successfully recover a CW wave at -80 dBm black box input power (-70 dBm for phase slip free operation), providing 20 dBm of output power from the injection locked slave laser.

Image encryption scheme based on optical chaos and DNA Rubik’s cube algorithm

In order to improve the complexity of optical chaotic sequence output and the encryption efficiency of bit plane encryption, an image encryption algorithm based on optical chaos and DNA Rubik’s cube scrambling is proposed. An external disturbance structure of light injection is proposed to improve the complexity of the chaotic sequence of light output from the slave laser by the external disturbance generated by the mutual injection between the driving laser and the main laser. Meanwhile, in the image algorithm, in addition to Rubik’s cube scrambling at the pixel level, this paper proposes a bit plane encryption method based on DNA plane Rubik’s cube scrambling, which reduces the amount of encrypted data and further improves the security of image encryption by using encryption selection of different DNA encoding modes. The scrambled images are diffused by DNA calculation and optical chaos sequence at the bit-level and pixel level respectively. Through the quantitative analysis of the security simulation of the proposed algorithm, the results show that the algorithm guarantees a certain encryption efficiency under the condition of good security, the key space is 1064, the information entropy of each test ciphertext image is close to the theoretical maximum, and the test indexes of plaintext sensitivity and key sensitivity are close to ideal values. For differential attacks, chosen plaintext attacks, known plaintext attacks, exhaustive attacks, cropping attacks, and noise attacks have good robustness.

Fiber laser strain sensor based on an optical phase-locked loop.

In this Letter, we present a high-strain resolution fiber laser-based sensor (FLS) by a novel optical phase-locked loop (OPLL) interrogation technique based on a root mean square detector (RMSD). The sensor consists of a distributed feedback (DFB) fiber laser as a master laser for strain sensing and a fiber Fabry-Perot interferometer (FFPI) as a reference. The laser carrier locks to the reference by the PDH technique, and the single sideband laser working as a slave laser locks to the DFB sensing element using the OPLL technique, respectively. A strain resolution of 8.19 pε/√Hz at 1 Hz and 35.5 pε in 10 s is achieved in the demonstrational experiments. Significantly, the noise behaves a 1∕f distribution below 0.2 Hz due to the very low pump power for the DFB sensor and an active thermostat testing environment. The proposed OPLL interrogation brings new thinking for the demodulation of FLS. This strain sensor based on FLS has a great performance in strain measurement and can be a powerful tool for geophysical research.

Cascaded optically injection-locked semiconductor laser, rate equations analysis, frequency response, and its application for complex optical signal generation.

In this paper, we introduce the concept of the cascaded optically injection-locked (OIL) semiconductor laser and present its novel rate equations. Then, the new locking range for this configuration has been obtained by mathematical demonstration. Subsequently, we modified a new adjustment for the detuning frequencies (Δ f i n j ) of the cascaded OIL system as well as the linewidth enhancement factors (α) values. Utilizing these tunings, improvements in the steady-state photon number and the phase modulation (PM) range become possible. Afterward, we define the generation of the complex optical signal area and extract the transfer function for investigating the frequency response of the cascaded system. The simulations have been performed once with identical α values and once with the various α values in the slave laser (SL) stages. We conclude that these novel proposed adjustments, combined with a strong injection ratio (Rinj) of 15 dB and a high bias current, can significantly broaden the bandwidth near 700 GHz while maintaining the fair gain available up to 180 GHz. Further, the generation of complex optical signal areas has been boosted for high-quality complex modulation applications. Eventually, we exhibit a novel approach for generating different α values in the SL stages by applying managed temperature variations in the experimental setup of the cascaded system, regardless of employing similar SLs.

Multi-Chirp Piecewise Linearly Frequency Modulated Microwave Generation Using a Semiconductor Laser

A simple structured photonics-based multi-chirp piecewise linearly frequency modulated microwave (Ph-MPLFM) waveform is proposed and demonstrated experimentally for radar systems. The proposed technique consists of a master laser which is injected into a typical slave laser, distributed feedback (DFB) laser, with a negative wavelength detuning for the radio frequency (RF) signal generation. The frequency of the generated RF signal is varied by implementing the redshift phenomenon in the emission wavelength of the slave laser. We introduced a series of piecewise arbitrary waveform with different amplitude-time slopes to obtain the controlled redshift of an emission wavelength of a DFB laser. In this work, two- and three-chirp LFM waveforms are demonstrated. The generated Ph-MPLFMs have a total time period of 1 μs with equal sub-interval periods. The generated two-chirp Ph-MPLFM has chirp rates of 6 GHz/μs and 10 GHz/μs. The chirp rate and the number of chirps can be reconfigured by modifying the applied piecewise arbitrary wave generator (AWG) signal to the intensity modulator. As part of reconfigurability, two and three-chirp PH-MPLFMs with different chirp rates, 3 GHz/us, 15 GHz/us, and 3 GHz/us; and 6 GHz/μs, 15 GHz/μs, and 3 GHz/μs are demonstrated. The generated Ph-MPLFM has the FWHM and Doppler resolution of 120 ps and 0.7 MHz for three-chirp waveforms. Hence, the proposed Ph-MPLFM radar waveform can be used as a promising and robust radar waveform in multi-radar environment applications.

A Wavelength Tunable Multi-Section PIC as an Upstream Transmitter for TWDM Networks

In this paper, we demonstrate a novel multi-section directly modulated laser transmitter for upstream operation in the application of time wavelength division multiplexing (TWDM) architecture. The photonic integrated circuit (PIC) is fabricated using a regrowth-free process that favors simplified and fast manufacturing. The PIC is based on a master-slave configuration, with an addition of a variable optical attenuator (VOA) section between them, and a semiconductor optical amplifier (SOA) at the output. The VOA enables control of the optical injection from the master to the directly modulated slave laser improving the transmission performance. The integrated SOA section at the output is used to boost or turn off the optical output power of the transmitter, thereby enabling burst mode operation. Experimental results show that the PIC can be tuned to four wavelength channels on a 100 GHz frequency grid. We also demonstrate that each channel achieves error-free performance (bit error ratio < 10e <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-9</sup> ), when modulated with 10 Gbps signal and transmitted over 25 km and 50 km fiber. The SOA-based output disable feature of the PIC delivers more than 60 dB attenuation.

High-precision digital optical phase locking for 10-12 W order weak light for a spaceborne gravitational wave interferometer.

We developed a digital optical phase-locking loop (DOPLL) for weak light phase locking in spaceborne gravitational wave interferometers (SGWIs). Using the system, we successfully locked the phase of the slave laser to the master laser with the power of only several picowatts, much smaller than the LISA requirement (100pW). The system does not introduce steady-state errors, and the Bode diagram shows its stability. The out-loop phase noise floor (2.3×10-4 and 5.2×10-4 r a d/H z 1/2) is very close to the shot noise limit. The Allan standard deviation of the heterodyne signal reaches 3.1×10-17 at 1000s. With the previous automatic locking program designed by other researchers, the results demonstrate that DOPLLs have bright application prospects and can be applied in the transducer of the SGWI.

An injection-locking diode laser at 671 nm with a wide tuning range up to 6 GHz

We present a compact injection-locking diode laser module to generate 671 nm laser light with a high output power up to 150 mW. The module adopts a master–slave injection-locking scheme, and the injection-locking state is monitored using the transmission spectrum from a Fabry–Pérot interferometer. Beat frequency spectrum measurement shows that the injection-locked slave laser has no other frequency components within the 150-MHz detection bandwidth. It is found that without additional electronic feedback, the slave laser can follow the master laser over a wide range of 6 GHz. All the elements of the module are commercially available, which favors fast construction of a complete 671-nm laser system for the preparation of cold 6Li atoms with only one research-grade diode laser as the seeding source.

Controlling the likelihood of extreme events in an optically pumped spin-VCSEL via chaotic optical injection.

We report on the manipulation of extreme events (EEs) in a slave spin-polarized vertical-cavity surface-emitting laser (spin-VCSEL) subject to chaotic optical injection from a master spin-VCSEL. The master laser is free-running but yielding a chaotic regime with obvious EEs, while the slave laser originally (i.e., without external injection) operates in either continuous-wave (CW), period-one (P1), period-two (P2), or a chaotic state. We systematically investigate the influence of injection parameters, i.e., injection strength and frequency detuning, on the characteristics of EEs. We find that injection parameters can regularly trigger, enhance, or suppress the relative number of EEs in the slave spin-VCSEL, where the large ranges of enhanced vectorial EEs and average intensity of both vectorial and scalar EEs can be achieved with suitable parameter conditions. Moreover, with the help of two-dimensional correlation maps, we confirm that the probability of occurrence of EEs in the slave spin-VCSEL is associated with the injection locking regions, outside which enhanced relative number of EEs regions can be obtained and expanded with augmenting the complexity of the initial dynamic state of the slave spin-VCSEL.

An All-Optical Microwave Frequency Divider with Tunable Division Factors Based on DP-DPMZM

Based on a dual-polarization dual-parallel Mach–Zehnder modulator (DP-DPMZM), an all-optical frequency divider is proposed and experimentally demonstrated. Two radio frequency (RF) signals are modulated on an optical carrier to work as a dual-beam master laser (ML). The optical signals of the ML are injected into a distributed feedback (DFB) laser to initiate the period-two (P2) state oscillation. By beating the output of the slave laser (SL) via circulator in a photodetector, a frequency divider with tunable factors can be achieved. The innovation of the scheme lies in having a simple structure and only requires optical devices, which is operated in wide RF frequency range without any electrical amplifiers before the photodetector to increase the conversion gain. Experiment results also demonstrate that the frequency division factors can be adjusted.

Nonlinear Dynamics and Potential Application of a DFB Laser Subject to Dual-Beam Injection

This paper presents a detailed experimental investigation of the nonlinear dynamics of a dual-beam optically injected semiconductor laser. Unlike previous works, we focus on the situation where the power and the frequency of the injection light wave are fixed and the free running frequency of the laser subject to optical injection is in between the two injection beams that have a large frequency separation. The nonlinear dynamics of the slave laser (SL), i.e., the laser subject to optical injection, for different SL forward bias currents are examined. Results show, in addition to the regenerated injection light wave, a fundamental oscillation together with its harmonics are generated when the SL is interacted with its nearby injection beam. The SL output frequency components are stabilised when one of the harmonics of the fundamental oscillation is located at the injection beam that is far away from the free running SL. More than six-fold improvement in the frequency stability of the resultant output microwave signal, compared to that generated by optical mixing, is obtained. Experimental results also show the SL nonlinear dynamics have different behaviours when the two injection beams have different frequency separations.

High-energy, alignment-insensitive, injection-seeded Q-switched Ho:yttrium aluminum garnet single-frequency laser

Abstract A high-energy, alignment-insensitive, injection-seeded Q-switched Ho:yttrium aluminum garnet (YAG) single-frequency laser is developed. Both the slave Q-switched laser and the seed laser are Ho:YAG ring lasers based on a pair of corner cubic reflectors. The seed laser has an available power of 830 mW at 2096.667 nm. At 100 Hz, the Q-switched Ho:YAG laser provides a single-frequency pulsed output using injection-seeded technology. The 7.3 mJ single-frequency pulse energy from the slave laser has a pulse width of 161.2 ns and is scaled to 33.3 mJ after passing through the Ho:YAG single-pass amplifier. According to the measurement results of the heterodyne beating technique, the single-frequency pulse has a half-width of 4.12 MHz.

Evolution of extreme events in chaotic light-injected semiconductor lasers

&lt;sec&gt;Rare ultrahigh pulses, classified as rogue waves (RWs), are inevitable and catastrophic in many different systems. Considering the damage they may produce, it is meaningful to understand the formation mechanism of these pulses and, if possible, control them. However, the rarity of RW and the difficulty in implementing the experiment are major limitations to understanding their formation. In 2007, Solli et al. (Solli D R, Ropers C, Koonath P, Jalali B &lt;ext-link ext-link-type="uri" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://www.nature.com/articles/nature06402"&gt;2007 &lt;i&gt;Nature&lt;/i&gt; &lt;b&gt;450&lt;/b&gt; 1054&lt;/ext-link&gt;) introduced the concept of optical RW, i.e. extreme event (EE) by comparing the appearance of oceanic RWs with the propagation of light fields in optical fibers. After that, the research of EEs entered into a flourishing period and different optical systems were proposed to analyze the generation and origin of EEs. Linear system is one of the most widely studied EE systems, such as linear light propagation in glass fibers, random media, and linear interference models. In addition to the linear systems mentioned above, efforts have also been made to produce nonlinear systems of EEs, such as microstructure fibers and tapered gradient exponential nonlinear fibers. In these nonlinear systems, the formation mechanism of EE is studied by using the nonlinear Schrödinger equation. Recently, the EEs in semiconductor laser systems have received a great deal of attention. On the one hand, semiconductor lasers with rich dynamic properties provide a cheap and controllable platform for understanding and predicting EE. The behavior of EE, on the other hand, is a powerful tool for understanding the fundamental mechanism of different laser systems.&lt;/sec&gt;&lt;sec&gt;In this work, based on the EEs generated in a semiconductor laser with phase-conjugate optical feedback (the master laser, ML), we inject its output into another free-running semiconductor laser (the slave laser, SL) and discuss the evolution of EEs in the system by numerical simulation. Herein, we analyze the influence of injection parameters on EEs through the two-dimensional maps of the relative number of EEs in the injection-parameter space. It can be concluded that in an area of high correlation, the relative number of EEs in SL tends to be a stationary value close to that in ML, while it may be enhanced in some weakly correlated regions. The results demonstrate the possibility of controlling EEs by optical injection, which is beneficial to optimizing the performance of chaotic laser systems or expanding their application scope.&lt;/sec&gt;