Laser Optical Communication Research Articles

The Blue LED Nobel Prize: Historical context, current scientific understanding, human benefit

The Blue LED Nobel Prize: Historical context, current scientific understanding, human benefit

Quantum dot semiconductor optical amplifier/silicon external cavity laser for O-band high-speed optical communications

We report a hybrid integrated external cavity laser by butt coupling a quantum dot reflective semi- conductor optical amplifier and a silicon-on-insulator chip. The device lasers at 1302 nm in the O-band, a wave- length regime critical to data communication systems. We measured 18 mW on-chip output power and over 50- dB side-mode suppression ratio. We also demonstrated open eye diagrams at 10 and 40 Gb∕s. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires

Dynamic Single-Mode Lasers

The 40-year history of research on semiconductor lasers for high-speed long-distance optical fiber communications, so-called dynamic single-mode (DSM) lasers, is reviewed. DSM lasers include phase-shift distributed feedback (DFB) lasers, uniform DFB lasers, wavelength tunable (WT) distributed Bragg reflector lasers, WT distributed reflector lasers, and external reflector lasers. The vertical cavity surface emitting laser is also a type of DSM laser that is applied for rather short-distance communication. Photonic-integrated circuits with monolithic integration of DSM lasers with other devices, as well as photonic crystal lasers, have advanced significantly to support stable operation of photonic subsystems. The DSM laser is currently essential for most long-haul optical communications and transoceanic submarine cables, as well as medium-distance local area networks. Its application to sensing systems is another interesting area.

Mycobacterium tuberculosis DNA Detection Using Surface Plasmon Resonance Modulated by Telecommunication Wavelength

A surface plasmon resonance sensor for Mycobacterium tuberculosis (MTB) deoxyribonucleic acid (DNA) is developed using repeatable telecommunication wavelength modulation based on optical fiber communications laser wavelength and stability. MTB DNA concentrations of 1 μg/mL and 10 μg/mL were successfully demonstrated to have the same spectral half-width in the dip for optimum coupling. The sensitivity was shown to be −0.087 dB/(μg/mL) at all applied telecommunication wavelengths and the highest sensitivity achieved was 115 ng/mL without thiolated DNA immobilization onto a gold plate, which is better than the sensor limit of 400 ng/mL possible with commercial biosensor equipment.

Anisotropic waveguide theory for electrically tunable distributed feedback laser from dye-doped holographic polymer dispersed liquid crystal

Anisotropic waveguide theory is developed for electrically tunable distributed feedback (DFB) laser from dye-doped holographic polymer dispersed liquid crystal (HPDLC) grating. The period grating structure, optical anisotropy of the liquid crystal (LC) and practical light propagation path in the HPDLC have been considered. The emitted lasing wavelength is deduced on basis of the dielectric anisotropy of the LC, transverse-magnetic (TM) light wave propagation in the core layer and DFB laser theory. An experimental method to determine the tilt angle of the LC and the lasing behaviours under different electric fields are used to verify the validity of the anisotropic numerical analysis. The results show that a more accurate agreement between the theoretical calculations and the experimental data is achieved. The anisotropic numerical analysis presented here is very useful when designing and optimising tunable lasers for optical communications and integrated optics.

RETRACTED: A Novel Material for Laser Diodes of Optical Fiber Communication

Retracted paper: The conventional material for the optical fiber communication laser diode is based on InGaAsP, which might be substituted by a potential candidate, InGaAlN. The new active region material, InN, is introduced regarding to its crystal growth and characterization, including the structural, optical and electrical properties. This material is promising for providing good performance of temperature stability of the wavelength. In addition, it is environmentally friendly.

Study of the effect of repump laser on atomic line filter

The improvement in the performance of an atomic line filter (ALF) under the action of a repump laser is reported in the current experimental work. We address the issue of repumping by including an additional laser coupling the 5S1/2(F=1)→5P3/2(F′′=2,1,0) hyperfine levels whereas the optical filter action is exhibited through a pump–probe laser-induced excited state absorption {5S1/2(F=2)→5P3/2(F′=3)→5D3/2(F′′=3)} of the Rb87 atom. It is found that the application of the repump mechanism considerably influences the characterizing parameters (i.e., transmittance and width) of the ALF. To optimize the performance of the ALF, it is required to carefully choose the detuning and intensity of the repump laser for a fixed set of pump–probe combination. For this purpose, the effect of systematic change in detuning and intensity of the repump laser on the ALF signal is studied in detail. For example, it is experimentally found that ALF considerably benefits (∼30%) in transmittance from selective repumping of atoms. It is to be noted that, unlike earlier reports, where the frequency scale of the filter is calibrated with Faby–Perot etalons of comparatively larger free spectral range, the marking is done here with the help of double resonance optical pumping (DROP) signals. The DROP signals, which originate from two-photon coupling within the 5S→5P→5D hyperfine domain, also act as an indicator of the existing “Radiation Trapping” process in the cascade medium. The current study may help in improving the performance of narrow-bandwidth ALF, which is useful for free space optical communication systems and laser spectroscopy.

(Invited) MBE Growth of GeSn and SiGeSn Heterojunctions for Photonic Devices

Strained Ge and GeSn are potentially direct bandgap Group IV materials suitable for photonic devices. We have grown both Ge and GeSn with controlled degrees of strain and GeSn/SiGeSn heterojunctions by low temperature MBE which demonstrate high quality and excellent optical properties, including stimulated emission. Gain calculations show that quantum wells of either strained Ge or GeSn that are direct bandgap provide gain comparable to III-V materials and will produce useful, low threshold lasers for on-chip optical communications

Influence of temperature on divergence angle of a focal telescope used in laser optical communication

Divergence angle of antenna is an important parameter in laser optical communication. It determines the power of the receiver terminal. In this paper, the influence of temperature on the divergence angle is discussed. Theoretical analysis and experiment results demonstrate that the relationship between the variance of temperature and of divergence angle is linear.

Strong optical injection locked semiconductor laser for high bit rate chaotic optical communications

We present in this article how strong optical injection can produce chaotic dynamics in the output of the semiconductor laser that is preferable for perfect encrypted optical communication networks. Significant increase in the relaxation resonance frequency was found implying higher degree of enhancement in modulation bandwidth. Numerical investigations under the condition of strong optical injection locking of the slave laser shows that instabilities in the photon number was observed and had settled down after a time of in the order of carrier lifetime. The model presented can be used to extract the characteristic parameters of the injection locking for detuning of the system. Optimum value of nonlinear gain and linewidth enhancement factor were found to have an impact on the chaotic dynamics of the slave laser. A layout for optical communication network using Optisystem 7.0 simulation software with slave laser as a transmitter undergoing strong optical injection locking will be illustrated for high bit rate. Chaos at high modulation frequency in the output power of the slave had been established in the simulations predicting the validity of the model for secure optical communications.

The analysis of spatial light to Bragg fiber coupling ratio

On the basis of the electromagnetic field mode matching theory, the coupling efficiency ratio from spatial light to Bragg fiber is analyzed, which shows that the coupling efficiency ratio is related to the radius of focused facular, the core radius of Bragg fiber and wave number of the core. By optimizing the value of such parameters appropriately, the Bragg fiber coupling efficiency ratio can be improved. It is also important for the analysis of the coupling efficiency of Bragg fiber, which can be applied to the free optical communication system and laser radar system.

High performance InP-based quantum dash semiconductor mode-locked lasers for optical communications

High performance InP-based quantum dash semiconductor mode-locked lasers for optical communications

High performance InP-based quantum dash semiconductor mode-locked lasers for optical communications

Several applications are pushing the development of high performance mode-locked lasers: generation of short pulses for extremely high bit rate transmission at 100 Gb-s and beyond, all-optical cloc...

Pointing Error Effects on Free-Space Optical Communication Links in the Presence of Atmospheric Turbulence

The effects of pointing errors on the performance of a free-space optical laser communication system are studied. The log-normal and gamma-gamma irradiance probability density function models have been considered to include the effects of optical turbulence. An expression for the mean intensity under pointing fluctuations is derived. Results for ergodic and outage channel capacities are presented. Since the irradiance statistics vary with pointing fluctuations, a wave-optics-based approach is proposed to evaluate the capacity expressions. Although, in general, turbulence degrades communications link performance, it can reduce sensitivity to pointing errors by increasing the effective beam radius. Finally, we present analytical expressions for evaluating the bit-error-rate performance of the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</i> - <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</i> keying system in the presence of pointing errors, and provide error performance results.

A LiÉnard Oscillator Resonant Tunnelling Diode-Laser Diode Hybrid Integrated Circuit: Model and Experiment

We report on a hybrid optoelectronic integrated circuit based on a resonant tunnelling diode driving an optical communications laser diode. This circuit can act as a voltage controlled oscillator with optical and electrical outputs. We show that the oscillator operation can be described by Lienard's equation, a second order nonlinear differential equation, which is a generalization of the Van der Pol equation. This treatment gives considerable insight into the potential of a monolithic version of the circuit for optical communication functions including clock recovery and chaotic source applications.

Continuously tunable compact lasers based on thermo-optic polymer waveguides with Bragg gratings

Based on the thermo-optic tuning of a polymer waveguide Bragg reflector, we demonstrated a cost-effective tunable wavelength laser for WDM optical communications. The excellent thermo-optic effect of the polymer waveguide enabled direct tuning of the Bragg reflection wavelength by controlling the electrical power on a micro-heater. Wavelength tuning for 32 channels with 0.8 nm wavelength spacing was demonstrated as well as a continuous tuning with wavelength steps of 0.1 nm. To be qualified as a tunable laser for WDM-PON applications, wavelength stability within 0.15 nm was confirmed for an operating temperature range from -10 to 70 degrees C.

Investigation Into the Integration of a Resonant Tunnelling Diode and an Optical Communications Laser: Model and Experiment

A resonant tunnelling diode has been monolithically integrated with an optical communications laser [the resonant tunnelling diode (RTD-LD)] to form a simple optoelectronic integrated circuit (OEIC) that is a novel bistable device suitable for an optical communications system. The RTD-LD was based on a ridge-waveguide laser structure and was fabricated from an InAlGaAs-InP epi-wafer grown by molecular beam epitaxy; it emitted at around 1500 nm. Voltage controlled optical-electrical switching and bistability were observed during the characterisation of the RTD-LD - useful features for a fibre-optic communications laser. Optical and electrical simulations of the RTD-LD were carried out using the circuit simulation tool PSPICE. In addition, a discrete component version of the RTD-LD was constructed which exhibited optical power oscillations, and along with the results of the simulations, gave insight into the operating principles of the monolithically integrated RTD-LD.

Integration of a resonant tunneling diode and an optical communications laser

We report on the first integration of a resonant tunneling diode and an optical communications laser operating at around 1.5 μm. We demonstrate its low-frequency bistable operation and model its electrical characteristics.

Amplified-spontaneous-emission spectrum of the radiation field in surface-emitting DFB lasers

In this paper, the authors calculate the amplified-spontaneous-emission spectrum of the radiation field in surface-emitting distributed feedback (DFB) lasers. The response of the laser cavity to the Langevin noise source in the frequency domain is obtained using the newly developed Green's functions for the slowly varying amplitudes of the guided waves. The authors show that the power spectra from the surface and the edge are different, and this discrepancy is due to excitation of the radiation field by the interference between the counter-propagating waves inside the cavity. This feature can be properly exploited in the design of surface-emitting DFB lasers for optical communications.

Temperature stabilized 1.55 μm photoluminescence in InAs quantum dots grown on InAlGaAs/InP

We report on temperature stabilized photoluminescence centered around 1.55 μm in InAs quantum dots grown by molecular beam epitaxy on InP substrate using InAlGaAs as the matrix layer. The photoluminescence emission peak wavelength of quantum dot samples with 5.5 monolayers of InAs deposition has a near zero shift between 300 and 77 K measurements. Decreasing the deposited InAs layer thickness or introducing a GaAs strain-balance layer leads to a regular redshift in the photoluminescence emission with increasing temperature. On the contrary, a blueshift is observed on samples with a thicker InAs layer thickness. These phenomena indicate the strain around quantum dots plays an important role in deciding the temperature-dependent properties of the quantum dot samples. This interesting temperature stabilization of photoluminescence in the quantum dot samples offers great potential for optical communication laser applications.