Output Of Semiconductor Laser Research Articles

Performance Evaluation of Chaotic Semiconductor Laser

Abstract: Chaotic semiconductor lasers are produced for applications in long-distance communication and for concealing modulated messages. In the present work, the dynamics of chaotic behavior in semiconductor lasers utilizing optoelectronic feedback have been investigated using the Optisystem software. Different parameters are controlled to get the optimum chaotic laser. An external perturbation is applied to the semiconductor laser output that has two control parameters, which are frequency and amplitude. Modulation is achieved by the variation in perturbation bias injunction currents while the modulation peak current is fixed. The study employs a delayed optoelectronic feedback diode laser to assess the ability to achieve chaotic output from directly frequency-modulated semiconductor lasers. This is done under various GHz modulation conditions while maintaining a fixed bias current. Keywords: Chaos, Semiconductor laser, Optoelectronic feedback, Optical communication.

Current Mode Logic based Semiconductor Laser Driver Design for Optical Communication System

In optical communication systems, semiconductor lasers are widely in use as an optical source but the performance of laser are limited due to temperature variation, design incompetency, and power consumption issues. The direct output of semiconductor laser may destroy the additional component attached in the system. In this research, semiconductor laser, driver is implemented by utilizing the current mode logic technique to control the output of semiconductor laser. Current Mode Logic (CML) is one of the compatible technique to work integeratedly with optical components. CML based design of semiconductor laser driver has achieved the current ranges from 5.6 mA to 6.8 mA and efficiently working up to 10 GHz frequency and consume 75% less power than typically available laser drivers. In future, the semiconductor laser may have implemented using System on Chip (SoC) configuration to make the design more energy efficient, in terms of temperature sensitivity and power consumption.

The Facet Passivation Characteristic of 940nm Semiconductor Laser

A novel facet coating technology is presented by studying catastrophic optical mirror damage mechanism of semiconductor laser. In this technology, semiconductor laser are cleaved in the air, and the surface oxide layer is removed with a low energy ion source, immediately flowed by coating the facet with 20nm of thin ZnSe passivation layer. The function of the passivation layer is to protect semiconductor laser facet, and prevent impurity particles diffusing to the facet. Finally the facet is coated with oxidative optical film. The test results of semiconductor laser output power show that output power with the coated ZnSe passivation layer method is 12% higher than coated Si passivation layer, and 36% higher than that coated oxidative optical film. The device coated oxidative optical film is failed when current is 4.1A, and the device coated with Si passivation layer is failed when current is 4.8A, the final failed of the device is coated ZnSe passivation layer. In conclusion, the method of coated ZnSe passivation layer on the semiconductor laser facet can effectively prevent the catastrophic optical mirror damage, and increase the output power of semiconductor lasers.

Single photon wavelength modulation absorption spectrum of acetylene for 1.5 m laser wavelength stabilization

We describe a kHz single photon wavelength modulation technology to realize the locking reference signal of the laser frequency. By detecting the single photon acetylene gas absorption spectrum and by amplifying the lock-in the discrete single photon response pulse, we achieve the laser frequency stabilized in real time. The 1.5 m distribution feedback semiconductor laser output frequency is stabilized at acetylene gas absorption peaks, and the typical laser frequency fluctuation is less than 25 MHz within 175 s. This single photon wavelength modulated absorption spectrum technology eliminates the high background noise in low frequency range and can be used in the quantum communication system and optical wavelength division multiplex.

Chaos synchronization and encoding in coupled semiconductor lasers of multiple modulated time delays

We numerically investigate the synchronization performance of unidirectionally and bidirectionally coupled chaotic semiconductor lasers subject to multiple modulated time delays optical feedbacks. Moreover, by studying the autocorrelation function of the coherent feedback semiconductor laser output, we find that the signatures of time delays can be erased in systems incorporating modulated feedback time delays, which largely improve the system security. Finally, chaos masking switching (CMS) is utilized to examine the communication ability. Numerical results indicate that the messages could be successfully recovered both in unidirectionally and bidirectionally coupled lasers, which confirms the possibility of applying multiple modulated delay system in optical chaos secure communication.

All-digital pulse generator for gradually modulated semiconductor laser

an all-digital design method consisting of a laser drive circuit for gradually modulating the frequency, pulse width, and amplitude of the output of semiconductor laser is demonstrated. field programmable gate arrays (fpgas) and accurate delaying chip are used to generate the pulse. the repetition rate and pulse width of the laser pulse gradually adjust from 1 to 10 khz and 700 ps to 3 ns, respectively. furthermore, the time of the rising and falling edges for the laser pulse is less than 800 ps.

Erasure of time-delay signatures in the output of an opto-electronic feedback laser with modulated delays and chaos synchronisation

By studying the autocorrelation function of the opto-electronic feedback semiconductor laser output the authors establish that the signatures of time delays can be erased in systems incorporating modulated feedback time delays. This property is of importance for the suitability of such laser systems for secure chaos-based communication systems. The authors also make the first report on chaos synchronisation in both uni-directionally and bi-directionally coupled multiple time-delay chaotic semiconductor lasers with modulated opto-electronic feedbacks.

Improved time-resolved simulation of amplitude and phase fluctuations in semiconductor laser light

We present an algorithm designed to produce improved simulations of amplitude and phase fluctuations present in the light output of semiconductor lasers. The algorithm is based on the physical principle of operation of semiconductor lasers, and takes fully into account the correlation between amplitude and phase fluctuations, as well as partition noise at the laser output. The simulated results are shown to agree very well with theoretical, frequency-domain noise descriptions.

Off-axis mirror based optical system design for circularization, collimation, and expansion of elliptical laser beams

In this paper, we present two optical system design methods for beam circularization, collimation, and expansion of semiconductor laser output beam for possible application in LIDAR systems. Two different optical mirror systems are investigated: an off-axis hyperbolic/parabolic mirror system and an off-axis parabolic mirror system. Equations specific to these mirror systems are derived and computer package programs such as ZEMAX and MATLAB are used to simulate the optical designs. The beam reshaping results are presented.

In-line interferometer for direction-sensitive displacement measurements by optical feedback detection

We demonstrate a compact in-line interferometer for direction-sensitive displacement measurement by optical feedback detection with a semiconductor laser (SL) light source. Two reflected beams from a semitransparent reference mirror and a reflecting test object interfere in the SL medium, causing a variation in its output power. The reference mirror is located between the SL output facet and the test object. The performance of the interferometer is investigated numerically and experimentally to determine its optimal operating conditions. We have verified the operating conditions where the behavior of the SL output power profile could indicate accurately the displacement magnitude and direction of the moving test object. The profile behavior is robust against variations in optical feedback and scale of the interferometer configuration.

Analytical expressions, modeling, and simulations of intensity and frequency fluctuations in directly modulated semiconductor lasers

Analytical expressions for the intensity and frequency/phase noise of single-mode semiconductor lasers based on quantum- mechanical rate equations are derived. Correlated photons, electrons, and phase Langevin noise sources and their auto and cross-correlation relations are presented, along with a novel self-consistent normalized laser model that includes the laser's correlated noise sources. A symboli- cally defined device (SDD) is constructed using the proposed normalized model and implemented in Agilent's advanced design system (ADS) CAD tool. Dynamic laser characteristics are predicted using the SDD implementation for 1300-nm InGaAsP/InP lasers. The results of time do- main dynamic simulations of photons, carriers, optical output power, and phase—with and without the effects of noise—are presented. Simulation results are used to show the effects of random noise on both the phase and optical power output of semiconductor lasers. Simulation results are analyzed to demonstrate the resonance frequency shift dependence on the bias current levels, the relation between the frequency response and the bias current, and the dependence of the laser line width broadening on the frequency fluctuations. Comparison between the presented re- sults and other published results (simulations and measurements) show good agreement while achieving simulation time enhancement. The suit- ability of the proposed models for the study and characterization of the performance of complete systems in both circuit and system simulations is examined. © 2004 Society of Photo-Optical Instrumentation Engineers.

Frequency noise spectroscopy lineshape measurements and simulations for a semiconductor laser with strong optical feedback

Semiconductor lasers with strong optical feedback from a plane mirror, or a weakly dispersive diffraction grating, have a frequency noise spectrum that contains a number of noise modes at frequencies close to the modespacing of the external cavity. Experiments and simulations are presented which characterise the measurement of this frequency noise using absorption on an atomic transition. The frequency noise spectroscopy lineshapes are modelled, and characterised experimentally, as a function of the strength of the optical feedback to the semiconductor laser, the detection frequency, the longitudinal mode spacing of the laser system of semiconductor laser and external cavity, the Doppler width of the atomic transition used for detection, and the order of the noise modes. The comparison of simulations and experiment indicate that the measurements behave as expected when the laser system operates in a robust single mode, as determined by optical spectral analysis. The results reinforce the utility of frequency noise spectroscopy as a means of sensitively characterising the output of semiconductor lasers with optical feedback.

Multiple angle-tuned étalon filters for optical channel selection in wavelength-division multiplexed and optical frequency-division multiplexed direct-detection transmission systems

We propose and demonstrate the use of multiple angle-tuned in-line Fabry-Perot etalon filters for tunable optical channel selection in wavelength-division multiplexed and optical frequency-division multiplexed direct-direction fiber transmission systems. Feasibility is experimentally demonstrated with two stacked identical etalons [free spectral range (FSR) of 74 nm with a finesse of 50 for each etalon] and with two stacked nonidentical etalons (FSR of 8 and 2 nm, respectively, with a finesse of 76 for both etalons). The stacked etalons are used to select the individual modes of a multilongitudinal-mode semiconductor laser output in the 1550-nm region. The method allows the selection of tens or possibly hundreds of closely spaced optical channels, because the reduction of channel spacing to much less than 1 mm is feasible, and the resultant FSR of stacked nonidentical etalons can be made much larger than their individual FSR’s.

Kerr modulation of signals at 1.3 and 1.5 μm in polarisation-maintaining fibres pumped at 1.06 μm

Optically induced high-speed modulation of the output of semiconductor lasers at 1.3 and 1.5 μm has been achieved in polarisation-maintaining fibres pumped with the output from an Nd:YAG laser

Beyond mean field and plane wave theories of bistable semiconductor lasers

The steady-state output of semiconductor lasers containing saturable absorbers is calculated using a model that includes transverse mode variation, high gain and absorption coefficient, and high mirror transmission. The results are compared to the predictions of the mean field theory, and they show that the mean field formulas underestimate the amount of hysteresis and overestimate the required amount of absorption compared to the high gain formulas.

Instabilities in semiconductor lasers

Abstract One of the most relevant problems connected with optical fiber communication is that related to the presence of instabilities in the output of semiconductor lasers. These instabilities appear as nonlinearities in the optical power-current characteristic (kinks) or as dynamics instabilities (self-pulsing). These phenomena more frequently occur in devices without a refractive index profile introduced ad hoc in the junction plane (gain-guided lasers); self-pulsing, in particular, is present in aged lasers. Both of them, however, can appear also in nonaged lasers with lateral confinement of the e.m. field (index-guided lasers). In this paper the principal experimental results obtained studying instability phenomena and the physical mechanisms proposed for their explanation are reported and discussed.

Semiconductor laser output modulated in GHz frequency region observed by image tube streak camera

The image tube streak camera was applied to the observation of fast modulated continuous light signals. Intensity modulation of a semiconductor laser was observed up to 5 GHz.

Multimode fibre baseband frequency response measurement with single frequency output extracted from modulated InGaAsP laser

A new method to measure multimode fibre frequency response is presented by using a single longitudinal mode extracted from modulated semiconductor laser output. Intensity fluctuation noise, caused by r.f. modulation, is utilised as a broadband baseband signal. Baseband frequency response of a 1.98 km graded-index fibre is measured up to 1.5 GHz in 1.1–1.5 μm wavelength region. This method provides a simple and accurate measurement of intermodal dispersion excluding chromatic dispersion effect.

Time-dependent voltage measurement of pulsating AlxGa1−xAs double-heterostructure lasers

The optical pulsations in the output of semiconductor lasers are accompanied by a time variation of the diode voltage. During the optical pulse the voltage decreases by ≈2.5 mV, corresponding to a decrease in carrier population. In the interval between pulses the voltage recovers exponentialy with a 1.3±0.2-nsec time constant to its prepulse value as a result of carrier injection into the active region.

Reduction of Quantum Noise in Very Narrow Planar Stripe Lasers

Quantum noise observed in the light output of semiconductor lasers was dramatically reduced by making the stripe width narrower than 5 µm. The suppression of the shot noise resonance in the narrow planar stripe lasers (NPS laser) was qualitatively explained by the buffer effect brought about by the increased spontaneous emission which goes into the lasing modes. The increased spontaneous emission also plays a role to suppress the relaxation oscillation in the NPS laser. Neither the intensity fluctuation due to the self-pulsation nor the partition noise resulting from the transverse multimode oscillation was observed owing to highly uniform excitation and the excellent transverse-mode control in the NPS lasers.