Semiconductor Optical Amplifier Research Articles

Broadband chaos generation utilizing a wavelength-tunable monolithically integrated chaotic semiconductor laser subject to optical feedback.

We demonstrate a broadband and wavelength-tunable chaotic laser by using a monolithically integrated wavelength-tunable chaotic semiconductor laser subject to optical feedback. The chip consists of a gain section, a distributed Bragg reflection grating section, a semiconductor optical amplifier section, and a phase section. By applying an optical feedback loop to the chaotic semiconductor laser chip, a nonlinear frequency mixing is stimulated in the laser cavity, and the chaos bandwidth is expanded to 33.6 GHz, which is 4.4 times larger than the bandwidth without optical feedback. Furthermore, the effect of feedback optical power on the bandwidth is investigated. The results show that the wide power spectrum of chaotic laser is available in a large wavelength range from 1556.44 nm to 1566.42 nm. This work explores a broadband and wavelength-tunable chaotic semiconductor laser for the wavelength division multiplexing to enlarge the capacity in chaotic secure optical communications.

Influence of the linewidth enhancement factor on the signal pattern of Fourier domain mode-locked lasers

Fourier domain mode-locked (FDML) lasers are frequency-swept lasers that operate in the near-infrared region and allow for the attainment of a large sweep-bandwidth, high sweep-rate, and a narrow instantaneous linewidth, all of which are usually quite desirable characteristics for a frequency-swept laser. They are used in various sensing and imaging applications but are most commonly noted for their practical use in optical coherence tomography (OCT). An FDML laser consists of three fundamental components, which are the semiconductor optical amplifier (SOA), optical fiber, and the wavelength-swept optical bandpass filter. Due to the complicated nonlinear dynamics of FDML lasers that stems from the coaction of these three components, often the output signal of an FDML laser is corrupted by frequent power-dips of varying depth and duration. The frequent recurrence of these dips in the FDML laser signal pattern lowers the quality of imaging and detection. This study examines the role of the linewidth enhancement factor (LWEF) of an SOA in reducing both the strength and the number of power-dips throughout the FDML laser operation. The results are obtained using numerical computations that are in agreement with experimental data. The study aims to show that using SOAs with low LWEFs, the number of power-dips can be reduced for a better detection and imaging quality.

Revolution of optical computing logic gates based on its applications: an extensive survey

Nowadays, communication has grown into a key area with a rapidly growing user community. The existing broadband users are overcrowded, and its faster speed has now become an essential parameter to meet the consumer’s expectations in the growing technology. As a result of our growth in computer technologies, high-speed processors are necessary, which provide simultaneous data computing with lower costs and a performance of more than 10,000 times quicker than electrical computers. Optics has become a more feasible alternative to electronics because of its greater speed. In this study, various methods of photonic crystals (PhCs) have been thoroughly examined, with essential properties and their benefits explained over previously identified methods (semiconductor optical amplifier and nonlinear waveguides) utilized to construct all-optical logic circuits. Particularly, evaluated a number of articles that covered topics including self-collimation effects, PhC waveguide intersection, and multi-mode interference with nonlinear effects. The merits and demerits of each technology are analyzed. Finally, concluded the major difficulties and the potential usage of every method. PhCs are used in logic circuits and devices for high data transmission. The performances of different types of logic gates based on PhC are studied.

Output Characterization of 220 nm Broadband 1250 nm Wavelength-Swept Laser for Dynamic Optical Fiber Sensors.

Broadband wavelength-swept lasers (WSLs) are widely used as light sources in biophotonics and optical fiber sensors. Herein, we present a polygonal mirror scanning wavelength filter (PMSWF)-based broadband WSL using two semiconductor optical amplifiers (SOAs) with different center wavelengths as the gain medium. The 10-dB bandwidth of the wavelength scanning range with 3.6 kHz scanning frequency was approximately 223 nm, from 1129 nm to 1352 nm. When the scanning frequency of the WSL was increased, the intensity and bandwidth decreased. The main reason for this is that the laser oscillation time becomes insufficient as the scanning frequency increases. We analyzed the intensity and bandwidth decrease according to the increase in the scanning frequency in the WSL through the concept of saturation limit frequency. In addition, optical alignment is important for realizing broadband WSLs. The optimal condition can be determined by analyzing the beam alignment according to the position of the diffraction grating and the lenses in the PMSWF. This broadband WSL is specially expected to be used as a light source in broadband distributed dynamic FBG fiber-optic sensors.

Design and Analysis of an O+E-Band Hybrid Optical Amplifier for CWDM Systems.

Broadband amplification in the O+E-band is very desirable nowadays as a way of coping with increasing bandwidth demands. The main issue with doped fiber amplifiers working in this band such as the bismuth-doped fiber amplifier is that they are costly and not widely available. Therefore, a wideband and flat-gain hybrid optical amplifier (HOA) covering the O+E-band based on a parallel combination of a praseodymium-doped fiber amplifier (PDFA) and a semiconductor optical amplifier (SOA) is proposed and demonstrated through numerical simulations. The praseodymium-doped fiber (PDF) core is pumped using a laser diode with a power of 500 mW that is centered at a wavelength of 1030 nm. The SOA is driven by an injection current of 60 mA. The performance of the HOA is analyzed by the optimization of various parameters such as the PDF length, Pr3+ concentration, pump wavelength, and injection current. A flat average gain of 24 dB with a flatness of 1 dB and an output power of 9.6 dBm is observed over a wavelength range of 1270-1450 nm. The noise figure (NF) varies from a minimum of 4 dB to a maximum of 5.9 dB for a signal power of 0 dBm. A gain reduction of around 4 dB is observed for an O-band signal at a wavelength of 1290 nm by considering the up-conversion effect. The transmission performance of the designed HOA as a pre-amplifier is evaluated based on the bit-error rate (BER) analysis for a coarse wavelength-division multiplexing (CWDM) system of eight on-off keying (OOK)-modulated channels, each having a data rate of 10 Gbps. An error-free transmission over 60 km of standard single-mode fiber (SMF) is achieved for different data rates of 5 Gbps, 7.5 Gbps, and 10 Gbps.

InP integrated optical frequency comb generator using an amplified recirculating loop.

A novel realisation of photonically integrated optical frequency comb generation is demonstrated on indium phosphide (InP) using a generic foundry platform. The architecture, based on the amplified recirculating loop technique, consists of cascaded electro-optic phase modulators embedded within a short waveguide loop. While an injected continuous wave laser signal is recirculated by the loop, the modulators are driven with a modulation frequency corresponding to the round-trip loop length frequency. This results in many phase coherent, evenly spaced optical comb lines being generated. The choice of InP as an integration platform allows immediate optical amplification of the modulated signal by embedded semiconductor optical amplifiers, enabling loop losses to be compensated and expanding the comb across broad optical bandwidths. This approach reduces the requirement for external, high-power optical amplifiers, improving the compactness and power efficiency of the full system. The system was modelled to identify off-resonance behaviour, outlining limits in matching both the modulation frequency and seed laser frequency to the round-trip loop frequency for optimal comb line generation to be achieved. The experimental device occupied a fraction of the 6 x 2 mm2 InP chip and operated at round-trip loop frequencies of 6.71 GHz to produce 59 comb lines within a 20 dB power envelope. All comb lines exhibited strong phase coherence as characterised by low composite phase noise measurements of -105 dBc/Hz at 100 kHz. A second device is also presented with a shorter loop length operating at ∼10 GHz which generated 57 comb lines. Both loop configurations included short waveguide phase shifters providing a degree of tunability of the free spectral range with a tuning range of 150 MHz for small injection currents of < 2.5 mA.

99.35 Tb/s Ultra-wideband Unrepeated Transmission Over 257 km Using Semiconductor Optical Amplifiers and Distributed Raman Amplification

In optical fiber networks, unrepeated links are cost effective solutions to provide connectivity in challenging contexts that hinder the deployment of in-line amplifiers. Extending the optical bandwidth beyond the C-band with ultra-wideband (UWB) amplification schemes is a promising way to scale the wavelength division multiplexed (WDM) throughput of such single-span systems. In this paper, we report on the use of semiconductor optical amplifiers (SOAs) combined with distributed Raman pumping to enable 100 nm ultra-wideband unrepeated transmissions over a 257.5 km ultra low-loss, large effective area fiber span. Leveraging state-of-the-art digital signal processing, wavelength-adaptive modulation and soft-decision forward error correction (FEC) schemes, we demonstrate a record capacity-distance product of 25.6 Pb/s <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\cdot$</tex-math></inline-formula> km, with a net throughput of 99.35 Tb/s over 257.5 km, using 247×49 GBd channels in S-, C- and L-bands.

Study of the quantum-confined Stark effect in an unbiased [111]-oriented multi-quantum well semiconductor optical amplifier

In this paper, we present a procedure and model for determining the electric field Fwq that governs the quantum-confined Stark effect (QCSE) in each quantum well of an unbiased [111]-oriented InGaAs/InGaAsP multi-quantum well semiconductor optical amplifier (MQW-SOA) with a p-i-n diode structure. For a given input power value, we estimated the electric field Fwq by substituting into simple theoretical expressions the experimentally determined output power, some structural parameters, and the voltage provided by a digital multimeter operating in diode test mode connected between the electrodes of the amplifier. The model results were used to estimate the Stark shift of the MQW-SOA excitonic resonances, which were blue-shifted by 5.21 meV when the input power was varied from –15.9 to 5.17 dBm. The excellent agreement between the experimental and calculated results allowed the validation of the model. To the authors’ knowledge, this is the first time that it has been experimentally demonstrated the presence of excitonic resonances in an MQW-SOA and the blue shift that they exhibit when the input power alters the QCSE. Finally, we used our model to investigate the impact of simultaneously modifying the strain in the quantum wells and the p-i-n junction built-in electric field (Fpin) on the variability of Fwq with respect to the input power. In fact, for zero input power, by modifying Fpin, we compensate for the fluctuation that Fwq undergoes when the strain is altered. Every time the strain is changed, and Fwq is compensated, a new operating regime is obtained. We found that the larger the operating regime strain, the less input power is required to vary |Fwq| by a given amount. For the MQW-SOA used in this work, about half the input power would be required to induce a 1 MV/m change in |Fwq| if an operating regime with a strain of –1.52 replaced one with a strain of –1.33.

Computational investigation of all-optical NOR logic operation using carrier reservoir semiconductor optical amplifiers at 120 Gb/s

Computational investigation of all-optical NOR logic operation using carrier reservoir semiconductor optical amplifiers at 120 Gb/s

Q-switching pulse and mode-locked square-wave pulse generated in a fiber ring laser based on nonlinear polarization rotation

We observe anomalous modes including Q-switching pulses and mode-locked square-wave pulses generated in a dual-gain-media fiber ring laser based on nonlinear polarization rotation in a semiconductor optical amplifier. We disclose the evolution process between them, and present in detail the temporal and spectra profiles of the output pulses. We find that the width of the square-wave pulse can be varied continuously from 500 ps to 165 ns by increasing the semiconductor optical amplifier (SOA) current or rotating the polarization controllers in the ring. The width of the pulse varies along with the temporal profile and spectrum pattern, then we further analyse its width-energy curve. For the first time to our knowledge, when we change the parameter of the ring laser (polarization controllers or variable optical attenuator), the stationary point of the width-energy curve will be shifted to a different position so that change the tuneable range of the pulse width. In addition, the evolution (no peak power clamping effect) and the features (chair-like pulse profile) of the generated square-wave pulse are different than previous reported square-wave pulses. Thus, the proposed scheme can facilitate further investigations of the characteristics of pulse generation in fiber lasers. Additionally, it can also serve as a multi-functional optical source to generate square-wave and Q-switching pulses for potential applications.

Micro-transfer-printed narrow-linewidth III-V-on-Si double laser structure with a combined 110 nm tuning range.

In this work, we demonstrate for the first time a narrow-linewidth III-V-on-Si double laser structure with more than a 110 nm wavelength tuning range realized using micro-transfer printing (µTP) technology. Two types of pre-fabricated III-V semiconductor optical amplifiers (SOAs) with a photoluminescence (PL) peak around 1500 nm and 1550 nm are micro-transfer printed on two silicon laser cavities. The laser cavities are fabricated in imec's silicon photonics (SiPh) pilot line on 200 mm silicon-on-insulator (SOI) wafers with a 400 nm thick silicon device layer. By combining the outputs of the two laser cavities on chip, wavelength tunability over S+C+L-bands is achieved.

All-optical latches using carrier reservoir semiconductor optical amplifiers

Lightwave communication systems, optical random memories, and photonic encryption/decryption are important applications that rely on all-optical latches. For the first time, the carrier reservoir semiconductor optical amplifiers (CR-SOAs) are employed to simulate two basic optical latches, Set-Reset (SR) latch, and D Flip-Flop, at a data rate of 120 Gb/s. All-optical NAND and NOT logic operations are used to build these latches, which are implemented using Mach-Zehnder interferometers (MZIs) with CR-SOAs. In the presence of the amplified spontaneous emission noise, the variation of the output quality factor (Q-factor) against the CR-SOA key operating parameters is studied. This is achieved by exploiting and numerically solving a set of coupled partial differential equations that describe the CR-SOAs gain and phase dynamics when operated as nonlinear elements and embedded in MZIs. The results demonstrate that CR-SOAs-based MZIs can achieve a high Q-factor while implementing the logical SR latch and D Flip-Flop at a high speed of 120 Gb/s.

Optical-Frequency-Comb Generation Based on Single-Tone Modulation and Four-Wave Mixing Effect in One Single Semiconductor Optical Amplifier

We propose a novel optical-frequency-comb (OFC) generation scheme based on single-tone modulation and the four-wave mixing (FWM) effect in one single semiconductor optical amplifier (SOA) modulated by a radio frequency (RF) current. A comprehensive broad-band dynamic model, which considers single-tone modulation and the FWM effect, is presented. The simulated results show that, although only one single continuous-wave light is input into the SOA, an OFC with a large number of frequency components can be achieved as a result of single-tone modulation and the FWM effect in the SOA. The number of comb lines and the spectral bandwidth of the OFC increase by raising the amplitude of the RF modulation current. Increasing the input light power can increase the average optical power of the OFC. The frequency interval is tunable within a certain range by tuning the frequency of the RF modulation current injected into the SOA.

Sampling Parallel SOA-MZIs Configuration for All-Optical Simultaneous Frequency Down-Conversion

In this paper, we expound a modulation concept to contrive simultaneous frequency down-conversion based on a three parallel Semiconductor Optical Amplifier Mach-Zehnder Interferometers (SOA-MZIs) link by using a band pass sampling method in a Virtual Photonics Inc. simulator. Each SOA-MZI is deployed to achieve a down-converted signal, which has ten replicas related to the first ten harmonic ranks of the sampling signal, at the SOA-MZI outer port. Then, the admixture of the three down-converted signals yields a sampled signal, which is called a simultaneous down-converted signal that contains thirty different replicas. The positive down-conversion gains with top values are reached with the sampling parallel SOA-MZIs link. Moreover, we evaluated the quality of the parallel SOA-MZIs transmission system over orthogonal frequency division multiplexing (OFDM) complex modulated signals using the error vector magnitude values as a performance index. The utmost bit rate attained is 2 Gbit/s for OFDM modulations.

Wave mixing efficiency in InAs/GaAs semiconductor quantum dot optical amplifiers and lasers

The nonlinear features of both semiconductor optical amplifiers (SOAs) and semiconductor lasers, which are made from the same InAs/GaAs quantum dot (QD) wafers, are investigated in detail. By employing pump-probe driven four-wave mixing as an experimental tool, the wave conversion process shows notably different profiles for the two types of devices. Due to the contributions of ultrafast, sub-picosecond mechanisms, such as carrier heating and spectral hole burning, the pump-probe frequency can be easily tuned to the THz range. SOAs generally benefit more from sub-picosecond carrier dynamics, hence exhibiting a higher conversion efficiency (CE) in the THz range, compared to their laser diode counterparts. The discrepancy even exceeds 10 dB. In addition, laser experiments yield some differences from the amplifier ones, hence leading to a higher nonlinear CE at small detuning ranges. These results strongly improve our insight into the fundamental nonlinear properties of InAs/GaAs QD material, and contribute to the conception of novel devices for future on-chip applications in all-optical communication networks, such as signal wavelength conversion, mode-locking, and optical frequency comb generation.

Design and Analysis of Novel O-Band Low Polarization Sensitive SOA Co-Integrated With Passive Waveguides for Optical Systems

Low polarization-dependent semiconductor optical amplifiers (SOAs) with an easy fabrication process and the capability to be co-integrated with passive elements are crucial in photonic integrated circuits. In this work, we design, simulate, and optimize a low polarization-dependent bulk SOA based on a novel layerstack with an unstrained bulk active layer with a robust and easy fabrication process that allows the co-integration with passive waveguides. The designed layerstack shows that the reflection between SOA and the passive waveguide is less than 1.3 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−5</sup> . Furthermore, by designing the ridge waveguide and layerstack (thickness of the core and cladding layers), the confinement factor of TE- and TM- modes (Г <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TE</sub> / <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TM</sub> ) are engineered to be approximately the same. This results in a low polarization-dependent SOA (since for the active bulk layer, the material gain of TE-mode is very close to the material gain of TM-mode). Numerical assessment of different length SOAs in terms of gain, polarization-dependent gain (PDG), noise figure are extensively investigated. Moreover, a booster SOA (1100 μm) with higher output saturation power has been investigated by widening the width of SOA from 1 μm to 3 μm. The output saturation power at 10 kA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> increases from +7.6 dBm to +13.9 dBm, when the width of the SOA waveguide increases from 1 μm to 3 μm. Finally, we discuss the fabrication tolerance on SOA characteristics. We show that the PDG strongly depends on the cladding layer thickness tolerance and decreases from 2.3 dB to 1.3 dB as it changes from 135 nm to 175 nm.

Direct determination of the piezoelectric field using the quantum-confined Stark effect in a strained [111]-oriented zinc-blende MQW-SOA

Here, we present a method, based on Stark shifts induced by the quantum-confined Stark effect, to directly determine the piezoelectric field in strained zinc-blende quantum wells (QWs) grown along the 111 direction and embedded in the p–i–n diode structure (p-iMQW-n) of a semiconductor optical amplifier. Under short-circuit and open-circuit conditions and resonant optical excitation, we experimentally determine the energy of the 1s e-hh excitonic resonance and the potential difference across the p-iMQW-n junction. Using these parameters in an analytical expression derived in this work, we directly determined a piezoelectric field of −108.71 ± 8.51 kV/cm acting on each of the eight 12-Å-wide strained [111]-oriented In0.687Ga0.313As /In0.807Ga0.193As0.304P0.696 QWs of a semiconductor optical amplifier (SOA). The theoretical prediction of −112.24 kV/cm was in very good agreement, within the experimental error, with the value of the piezoelectric field extracted through the proposed procedure, which was also indirectly validated by comparing the experimental value of the 1s e-hh excitonic resonance Stark shift with the extracted one. Even though the implemented technique was specially designed to experimentally determine the piezoelectric field acting on each of the QWs of a multiple quantum well SOA, it can be applied to any p–i–n structure with electrodes and strained [111]-oriented zinc-blende QWs embedded in its intrinsic region. Remarkably, the method proposed here allows direct experimental determination of the piezoelectric field through an analytical expression, with which it is also possible to estimate, with high reliability, the precision of the result and how it is affected by the accuracy of each measuring instrument intervening in the procedure.

XPoM-based 8-port photonic interconnection with low polarization sensitivity utilizing S–E–S hybridization

In this paper, we propose a hybrid amplifier-based 8-port Cross-Polarization Modulation (XPoM) interconnection with low polarization sensitivity unlike conventional Semiconductor Optical Amplifier (SOA)-based switching. The three-stage configuration utilizes Erbium-Doped Fiber Amplifier (EDFA) as an intermediate stage to reduce the effects of inherent polarization modulation creating large Transverse Electric – Transverse Magnetic (TE–TM) relative phase shifts. The appreciable error rate of [Formula: see text] and Extinction Ratio (ER) of 14.166 dB have been obtained with 100 GHz of port-spacing at different input powers. The low Polarization-Dependent Loss (PDL) of 1.0045 dB, small variations of azimuth and ellipticity with device angle in S–E–S configuration in contrast to that of SOA, adds to the superiority of the proposed model.

Optical transceiver communication systems performance evaluation based on nonlinear cross gain modulation effects

Abstract The aim of study is to simulate the impact of nonlinear cross gain modulation effects on optical transceiver communication systems with wide band traveling wave semiconductor optical amplifiers (WBTWSOAs). The max Q and electrical power against active amplifier length variations are simulated without/with nonlinear cross phase modulation (XPM) effect. We have been simulated the optimum Q Factor and BER at various data rate up to 160 Gbps with nonlinear cross phase modulation effect at the optimum active amplifier length of 300 μm. Also the optimum sig. power versus time and spectral wavelength is clarified with nonlinear CPM effect at the optimum active amplifier length. The total electrical power (TEP) and total optical power (TOP) are reported with nonlinear CPM effect at the optimum active amplifier length.

Directly extract optical clock from NRZ-PRBS data by SOA-based ultrahigh-order mode locking

We propose a scheme of all-optical clock recovery (AOCR) based on ultrahigh-order mode locking by a semiconductor optical amplifier (SOA), which can directly extract the optical clock from non-return-to-zero (NRZ) pseudo-random-binary-sequence (PRBS) data. Firstly we demonstrate that the active mode locking system can generate stable high repetition frequency ultrashort pulse train, and adjusting the modulator’s bias voltage and polarization states one can realize doubling the repetition frequency. Due to robust mode locking configuration, we successfully realize the AOCR up to 40 Gbits/s from the PRBS (231-1) NRZ optical signals without NRZ to RZ conversion, while the signal to noise ratio of the recovered optical clock is more than 20 dB with high stability, and the pulse width is short as 1.85 ps. Owing to the ultrafast nonlinear polarization rotation in the SOA, our scheme can execute AOCR for data rate of 100 Gbits/s and more.