Modulated Semiconductor Lasers Research Articles

Modulation Bandwidth Enhancement of Monolithically Integrated Mutually Coupled Distributed Feedback Laser

Modulation bandwidth enhancement of directly modulated semiconductor lasers (DMLs) has attracted broad interest to accommodate the tremendously growing demand for network traffic. In this paper, a monolithically integrated mutually coupled (IMC) laser for the O-band is demonstrated both numerically and experimentally. The direct modulation bandwidth was enhanced utilizing a photon–photon resonance (PPR) effect based on the mutual injection-locking technique. The IMC laser consisted of two distributed feedback (DFB) laser sections with a semiconductor optical amplifier (SOA) section in between. The relationship between the PPR frequency and SOA length was analyzed numerically to achieve a flat modulation response by optimizing the SOA length. Then, an enhanced 3-dB bandwidth of 38.7 GHz was realized experimentally, a nearly threefold enhancement over the modulation bandwidth of a solitary DFB laser at the same bias. Moreover, clear open eyes up to 40 Gb/s transmission over a 25-km single-mode fiber were achieved. Although the dynamic extinction ratio of the eye diagram was 1.1 dB, it can be further improved by increasing the mutual injection locking range of the IMC laser.

Applicability of small-signal laser and fiber models for passive optical networks operating at the 1550 nm window

Abstract Small-signal techniques are a useful engineering tool to estimate system performance, though small-signal models need to be tested against the large-signal from which they are derived. We show that combined small-signal models for lasers and optical fiber are valid for passive optical networks employing directly modulated semiconductor lasers, provided that the modulation extinction ratios are

Single emitter high power semiconductor laser module using vacuum sintering method

Based on the research of vacuum sintering technology, we developed a single-emitter high-power semiconductor laser module. The effects of the modules sintered under different conditions of temperature, pressure and time on the reliability of the device are proposed. The control variable is used to analyze the basic parameters of the multi-group modules. The optimal vacuum sintering method is evaluated and finally determined. Semiconductor laser modules sintered at a temperature of 270℃ for 100 s and the pressure of 20 g enjoy the best stability and reliability.

Time-resolved frequency chirp control of semiconductor lasers using digital signal processing

The theoretical possibility of precisely controlling the time-resolved chirp in a directly modulated semiconductor laser using a single drive digital-to-analog converter (DAC) controlled via a novel digital signal processing (DSP) algorithm is investigated. A semi-analytical expression for the requisite drive current is obtained through algebraic back-calculation of the large signal laser rate equations, in tandem with a first-order numerical approximation of the optical power and chirp functional relationship. A 25-GHz peak-to-peak frequency modulation (FM) at a bit-rate of 28-Gb/s is demonstrated at a 6 dB extinction ratio, while completely suppressing the transient chirp contribution. Furthermore, a bipolar frequency chirp signal resulting in a differential phase shift keying (DPSK) modulation format at a bit-rate of 28-Gb/s was achieved with an error vector magnitude (EVM) below 1%. A 5-bit look-up table (LUT) was found to be adequate for capturing the requisite DSP drive current needed to fully suppress the transient chirp as demonstrated by preliminary optical link simulations at 28-Gb/s.

Ultra-flat supercontinuum from 1.95 to 2.65 µm in a nanosecond pulsed Thulium-doped fiber laser

Abstract We report on mid-IR supercontinuum generation in an all-silica nanosecond pulsed fiber laser. The laser topology is a master oscillator power amplifier which consists of a two stage Thulium-doped fiber amplifier seeded with a directly modulated semiconductor laser at 1952 nm. The supercontinuum performance is investigated for repetition rate frequencies between 35 kHz and 100 kHz and pulse widths between 6 ns and 21 ns. Supercontinuum average output powers greater than 1.5 W and spectra ranging from 1.95 µm to 2.65 µm are demonstrated.

Measuring the frequency response of optically pumped metal-clad nanolasers.

We report on our initial attempt to characterize the intrinsic frequency response of metal-clad nanolasers. The probed nanolaser is optically biased and modulated, allowing the emitted signal to be detected using a high-speed photodiode at each modulation frequency. Based on this technique, the prospect of high-speed operation of nanolasers is evaluated by measuring the D-factor, which is the ratio of the resonance frequency to the square root of its output power(fR/Pout1/2). Our measurements show that for nanolasers, this factor is an order of magnitude greater than that of other state-of-the-art directly modulated semiconductor lasers. The theoretical analysis, based on the rate equation model and finite element method simulations of the cavity is in full agreement with the measurement results.

Retraction Note to: Mode-competition phenomena among longitudinal modes in semiconductor lasers under the effect of external optical feedback

The authors have retracted the original article because the article shows significant overlap.

RETRACTED ARTICLE: Mode-competition phenomena among longitudinal modes in semiconductor lasers under the effect of external optical feedback

RETRACTED ARTICLE: Mode-competition phenomena among longitudinal modes in semiconductor lasers under the effect of external optical feedback

Almost perfect in-phase and anti-phase chaotic and periodic phase synchronization in large arrays of diode lasers

Abstract In this paper we study phase synchronization in large arrays of weakly coupled single mode semiconductor laser diodes. We show that if the coupling topology is chosen appropriately, the laser array exhibits robust phase synchrony (including chaotic and non-chaotic phase synchrony). Furthermore, one can define coupling topologies that lead to chaotic anti-phase synchronization. To the best of our knowledge, chaotic anti-phase synchronization has not been observed in large arrays of coupled nonlinear oscillators. When diodes are coupled via a decayed non-local coupling scheme, the leading spatial mode can be stable. This leads to an almost-perfect phase synchronous state where the phases are synchronized, but the system is not set exactly on the synchronization manifold. This almost-perfect phase synchronous state is robust to noise and frequency disorder and can be realized under periodic (fixed-intensity limit cycle) continuous-wave and chaotic behavior. The presented result is an example of the broader phenomenon of linear transverse mode selection taking place in a coupled oscillator system with nonlinear dynamics.

Single mode semiconductor laser based on coupled cavities of an active ring laser and Fabry Perot

A single mode laser based on coupled cavities of an active ring laser and a Fabry Perot is presented. The laser exhibits tunable single mode behaviour with a side mode suppression ratio of 41 dB and a line-width of 400 kHz.

Dependence of spectral characteristics of semiconductor and solid state lasers of visible range on active environment temperature

We consider research results on the effect of the active medium temperature, which varies with the operation of semiconductor and solid-state (DPSS) lasers of the visible range, on the output spectral characteristics. The paper presents the study results of the spectral-optical radiation parameters of semiconductor lasers, their coherence lengths, and the dependence of the spectral maximum position on temperature. This study is necessary for selection of the most optimal laser, which in the future is planned to be used in medical ophthalmologic diagnostics. The experiment was carried out by solid-state (DPSS) and semiconductor laser modules based on a laser diode. Spectral dependences on the active medium temperature of lasers were obtained, ranging from 300 to 370 K. The spectra were recorded with the use of an automated spectral complex based on the MDR-23 monochromator. We show determination possibility of the internal stabilization damage of laser modules without mechanical intervention but only by applying their spectral characteristics. The obtained data give the possibility to take into account the temperature characteristics and perform further optimization for parameters of such lasers

High precision linear frequency modulation ranging system based on semiconductor laser

Based on the linear frequency modulation (LFM) of semiconductor laser, a laser ranging system is built. The ranging precision of the system is about micron dimension with the repetition frequency of 100 kHz and a distance of 1–10 m. We analyzed the ranging precision experimentally. As the bandwidth increases, the ranging precision becomes higher and higher. When the bandwidth is fixed, as the distance increases, the signal-to-noise ratio (SNR) will decrease, which reduces the precision.

Quality Parameters of Zero-Order Bessel Light Beams

A collimated light beam at the output of a semiconductor laser module was studied experimentally. The intensity distribution in the transverse cross section of this beam did not have infinite-order axial symmetry and varied with the longitudinal coordinate. The experimental spatial intensity distributions in light fields formed by a conical lens (axicon) from radiation of He–Ne and semiconducting lasers were compared. Criteria were proposed for objective numerical quality assessment of zero-order Bessel light beams. The quality parameters of Bessel light fields formed by the axicon from radiation of He–Ne and semiconducting lasers were obtained from trial calculations.

МЕТОДЫ АВТОДИННОЙ ИНТЕРФЕРОМЕТРИИ РАССТОЯНИЯ ПРИ ТОКОВОЙ ЧАСТОТНОЙ МОДУЛЯЦИИ ПОЛУПРОВОДНИКОВОГО ЛАЗЕРА

МЕТОДЫ АВТОДИННОЙ ИНТЕРФЕРОМЕТРИИ РАССТОЯНИЯ ПРИ ТОКОВОЙ ЧАСТОТНОЙ МОДУЛЯЦИИ ПОЛУПРОВОДНИКОВОГО ЛАЗЕРА

Directly Modulated Semiconductor Lasers

This paper presents a review and discussion of the directly modulated semiconductor lasers and their applications to optical communications and microwave photonics. A detailed and comprehensive demonstration of directly modulated semiconductor lasers from development history to specific techniques on measurement, analysis, and packaging is provided for the first time to the best of our knowledge. A few typical applications based on directly modulated lasers are also illustrated, such as optical fiber communications, free-space optical communications and microwave photonics. Future directions of research are also highlighted.

Experimental demonstration of a hybrid integrated dual-parallel modulated DFB semiconductor laser with suppressed nonlinear distortions

A hybrid integrated dual-parallel modulated DFB laser is experimentally demonstrated. Utilizing the proposed method, the nonlinear distortions of the DFB laser, including the second harmonic distortion (2HD) and the third-order intermodulation distortion are suppressed significantly. Comparing with the single modulated DFB laser, the 2HD is reduced by 8.6 dB and the spurious free dynamic range is increased from 87.2 dB·Hz2/3 to 90.3 dB·Hz2/3.

A Hybrid Integrated Short-External-Cavity Chaotic Semiconductor Laser

A simple design of a hybrid integrated short-external-cavity chaotic semiconductor laser module is presented and fabricated. A distributed feedback laser chip is directed to the transflective mirror through a collimating micro-lens, and a part of the light is reflected by the mirror into the laser chip to induce chaos. Transmitted through the mirror, the generated chaotic light is coupled into a pigtail fiber as output by a focusing micro-lens. It should be pointed out that the part between the transflective mirror and the emitting surface of the chip works as a short external straight feedback cavity. All the components above together with chip submount, heat sink, and thermoelectric cooler are encapsulated by a commercial 14-pin butterfly package. In our experimental fabrication, the intensity reflectivity of the transflective mirror is optimized as 5% and the external-cavity length is 2 mm. Experimental tests show that chaotic light with a bandwidth larger than 4.5 GHz is readily obtained from the chaotic laser module by adjusting laser bias current.

Dual-frequency GaAs/InGaP laser diode with a GaAsSb quantum well

The results of investigation of a metal-organic-vapor-phase-epitaxy-grown GaAsSb/GaAs/InGaP laser structure are presented. Steady two-band generation caused by spatially direct and indirect optical transitions is obtained. Observation of the sum frequency shows the effective intracavity mixing of modes in semiconductor lasers of such a type.

Ultra-wideband Butterfly Directly Modulated Semiconductor Lasers

In this paper, a simple and cost-effective packaging scheme for improving the modulation bandwidth of directly modulated laser is presented and demonstrated. Combined with the equivalent circuit, the effect of disequilibrium on signal injection efficiency is comprehensively and systematically studied. The simulation and measurement results have a good agreement, which show that the high frequency performance of module can be effectively improved with the proposed packaging scheme. Finally, employing the proposed packaging scheme, we achieve the 3-dB bandwidth of up to 32 GHz regarding the directly modulated semiconductor laser module with the butterfly package.

Ranging method based on linear frequency modulated laser

In this paper, we obtain target information about the distance between laser sources and targets based on the linear frequency modulated laser ranging system. We designed a specific experimental scheme for the ranging of linear frequency modulated semiconductor lasers based on heterodyne ranging experiment. Ranging precision can reach micron dimension and range resolution is about 0.002 m within the range of 1–40 m. The ranging method in this paper can apply to laser radars which could be used to capture target information, which is very helpful for tracking, identifying and extracting targets.