Distributed Feedback Semiconductor Laser Research Articles

Distributed feedback laser for biosensing applications.

We present an organic semiconductor distributed feedback laser biosensor and demonstrate its sensing capabilities. Optimization of the gain layer thickness to maximize the response to refractive index changes and bulk sensing results are shown. Desthiobiotin-avidin sensing assay results are also presented and the potential to perform multiple, repeated sensing measurements is demonstrated.

Experimental demonstration of a low-cost tunable semiconductor DFB laser for access networks

A low-cost tunable semiconductor distributed feedback (DFB) laser design in access networks is proposed and experimentally demonstrated. It covers 9 nm continuous tuning range by changing the temperature. The side mode suppression ratios are above 42 dB over the tuning range. The current and temperature coefficients of wavelength tuning are 0.0124 nm mA−1 and 0.0875 nm °C, respectively. The results indicate that the reconstruction-equivalent-chirp (REC) technique is promising to fabricate low-cost tunable DFB lasers meeting the requirement of wavelength-division-multiplexing passive optical networks (WDM-PONs). It should be also noted that the tuning range can be easily extended by using more sections.

Microwave Photonic Integrated Circuits for Millimeter-Wave Wireless Communications

This paper describes the advantages that the introduction of photonic integration technologies can bring to the development of photonic-enabled wireless communications systems operating in the millimeter wave frequency range. We present two approaches for the development of dual wavelength sources for heterodyne-based millimeter wave generation realized using active/passive photonic integration technology. One approach integrates monolithically two distributed feedback semiconductor lasers along with semiconductor optical amplifiers, wavelength combiners, electro-optic modulators and broad bandwidth photodiodes. The other uses a generic photonic integration platform, developing narrow linewidth dual wavelength lasers based on arrayed waveguide gratings. Moreover, data transmission over a wireless link at a carrier wave frequency above 100 GHz is presented, in which the two lasers are free-running, and the modulation is directly applied to the single photonic chip without the requirement of any additional component.

Diffraction-limited, 10-W, 5-ns, 100-kHz, all-fiber laser at 1.55 μm.

This Letter reports on an all-fiber-integrated master-oscillator, power amplifier system at 1.55 μm producing 5-ns, 100-μJ pulses. These pulses are generated at a 100 kHz repetition rate, corresponding to 10 W of average power. The seed source is a low-power, current-modulated, single-frequency, distributed feedback semiconductor laser. System output is obtained from a standard single-mode fiber (Corning SMF-28). Consequently, the beam is truly diffraction limited, which was independently proven by M2 measurements. Further increase of peak power is limited by onset of significant spectral broadening due to nonlinear effects, primarily four-wave mixing. Numerical simulations based on six-level rate equations with full position- and time-dependence were developed to model propagation of pulses through the amplifier chain. This capability allows minimization of the amplified spontaneous emission, which can be directly measured using a fast acousto-optic modulator to gate the pulses.

Range Finding and Fault Locating with Chaotic Signal

In this paper, we review our recent works on range finding and fault locating in optical network and wire with chaotic signal. Using a distributed-feedback semiconductor laser with optical feedback as chaotic source, we developed a prototype chaotic optical time domain reflectometer which can achieve a range- independent resolution of 4cm and measurable distance of about 70km. We further present the measurement of faults in the wavelength-division-multiplexing passive optical network (WDM-PON) by using a wavelength-tunable chaotic laser. Moreover, we also demonstrate the location of wire faults or impedance discontinuities with chaotic signal. Our results show that the fault location using wideband chaotic signal is a promising method of precise diagnoses for WDM-PON and electric cables.

Experimental investigation on the nonlinear dynamical states of DFB semiconductor lasers subject to dual-beam optical injection

The nonlinear dynamic behaviors of the distributed feedback semiconductor laser (DFB-SLs) subject to dual-beam optical injection are experimentally investigated. The results show that the outputs of a DFB-SL subject to dual-beam optical injection display much rich and more complex nonlinear dynamical behaviors compared with that of a DFB-SL subject to single-beam injection. By fixing the oscillated wavelengths of two injection optical beams and continuously changing injection strengths of two injection optical beams, the output optical spectra and power spectra of the DFB-SL under different injection strengths of dual-beam optical injection have been measured. On the basis of the optical spectra and power spectra, some typical dynamical states have been determined under three cases categorized as scenarios A, B and C. Finally, we give the distribution map of the dynamical states of DFB-SL in the parameter space of two injection strengths, and the regions for scenarios A, B and C have been indicated.

Organic semiconductor distributed feedback laser pixels for lab-on-a-chip applications fabricated by laser-assisted replication.

The integration of organic semiconductor distributed feedback (DFB) laser sources into all-polymer chips is promising for biomedical or chemical analysis. However, the fabrication of DFB corrugations is often expensive and time-consuming. Here, we apply the method of laser-assisted replication using a near-infrared diode laser beam to efficiently fabricate inexpensive poly(methyl methacrylate) (PMMA) chips with spatially localized organic DFB laser pixels. This time-saving fabrication process enables a pre-defined positioning of nanoscale corrugations on the chip and a simultaneous generation of nanoscale gratings for organic edge-emitting laser pixels next to microscale waveguide structures. A single chip of size 30 mm × 30 mm can be processed within 5 min. Laser-assisted replication allows for the subsequent addition of further nanostructures without a negative impact on the existing photonic components. The minimum replication area can be defined as being as small as the diode laser beam focus spot size. To complete the fabrication process, we encapsulate the chip in PMMA using laser transmission welding.

Organic semiconductor distributed feedback (DFB) laser as excitation source in Raman spectroscopy

As an application of organic semiconductor distributed feedback (DFB) lasers we demonstrate their use as excitation sources in Raman spectroscopy. We employed an efficient small molecule blend, a high quality resonator and a novel encapsulation method resulting in an improved laser output power, a reduced laser line width and an enhanced power stability. Based on theses advances, Raman spectroscopy on selected substances was enabled. Raman spectra of sulfur and cadmium sulfide are presented and compared with the ones excited by a helium-neon laser. We also fabricated a spectrally tunable organic semiconductor DFB laser to optimize the Raman signals for a given optical filter configuration.

Pump spot size dependent lasing threshold in organic semiconductor DFB lasers fabricated via nanograting transfer

Optically excited organic semiconductor distributed feedback (DFB) lasers enable efficient lasing in the visible spectrum. Here, we report on the rapid and parallel fabrication of DFB lasers via transferring a nanograting structure from a flexible mold onto an unstructured film of the organic gain material. This geometrically well-defined structure allows for a systematic investigation of the laser threshold behavior. The laser thresholds for these devices show a strong dependence on the pump spot diameter. This experimental finding is in good qualitative agreement with calculations based on coupled-wave theory. With further investigations on various DFB laser geometries prepared by different routes and based on different organic gain materials, we found that these findings are quite general. This is important for the comparison of threshold values of various devices characterized under different excitation areas.

High output power, fibre‐coupled distributed feedback lasers operating near 2.05 μm wavelength range

Single-mode operation of fibre-pigtailed distributed feedback semiconductor lasers in the 2.05 μm range has been demonstrated. The lasers are packaged inside standard butterfly modules with output powers in excess of 10 mW at the end of polarisation maintaining optical fibre. The fibre-pigtailed lasers show excellent sidemode suppression ratios ( > 50 dB) and have a mode-hop free tunability larger than 1 nm. The output of the optical fibre has linear polarisation with better than 20 dB extinction over the operating current and temperatures.

Simple dual-loop optoelectronic oscillator with a low spurious level

We successfully demonstrated a simple dual-loop optoelectronic oscillator (OEO) with reduced spurious tones by using dual-direct modulation of a multi-electrode distributed-feedback semiconductor laser. By simply modulating the two electrodes of the laser simultaneously through a short and a long fiber loop, we realized a dual-loop OEO with highly suppressed spurious tones without any additional sophisticated optical devices or loop configuration. Compared with a single-loop approach, the X-band OEO signal generated by using the proposed device and loop configuration exhibits highly-suppressed spurious tones (>50 dB) without sacrificing the OEO signal and gain performance.

Simulation of the Optimized Structure of a Laterally Coupled Distributed Feedback (LC-DFB) Semiconductor Laser Above Threshold

In this paper, the laterally coupled distributed feedback semiconductor laser is studied. In the simulations performed, variations of structural parameters such as the grating amplitude a, the ridge width W, the thickness of the active region d, and other structural properties are considered. It is concluded that for certain values ​​of structural parameters, the laser maintains the highest output power, the lowest distortion Bragg frequency δL and the smallest changes in the wavelength λ. Above threshold, output power more than 40mW and SMSR values greater than 50 dB were achieved.

Low-cost and wideband frequency tunable optoelectronic oscillator based on a directly modulated distributed feedback semiconductor laser

A novel scheme to realize a low-cost and wideband frequency tunable optoelectronic oscillator based on a directly modulated distributed feedback (DFB) semiconductor laser is proposed and experimentally demonstrated. In the proposed scheme, neither an external modulator nor an electrical filter is used, and no more than 25 dB of the electrical loop gain is required due to the high modulation efficiency of the relaxation oscillation frequency of the DFB laser. Microwave signals with frequency coarsely tuned from 3.77 to 8.75 GHz are generated by changing the bias current and operation temperature of the DFB laser. The single sideband phase noise of the generated 6.97 GHz microwave signal is measured to be -103.6 dBc/Hz at 10 kHz offset.

Experimental demonstration of a multi-wavelength distributed feedback semiconductor laser array with an equivalent chirped grating profile based on the equivalent chirp technology

We report, to the best of our knowledge, the first realization of a multi-wavelength distributed feedback (DFB) semiconductor laser array with an equivalent chirped grating profile based on equivalent chirp technology. All the lasers in the laser array have an identical grating period with an equivalent chirped grating structure, which are realized by nonuniform sampling of the gratings. Different wavelengths are achieved by changing the sampling functions. A multi-wavelength DFB semiconductor laser array is fabricated and the lasing performance is evaluated. The results show that the equivalent chirp technology is an effective solution for monolithic integration of a multi-wavelength laser array with potential for large volume fabrication.

A novel concavely apodized DFB semiconductor laser using common holographic exposure

A novel concavely apodized (CA) distributed feedback (DFB) semiconductor laser was theoretically analyzed and experimentally demonstrated. The CA grating profile is equivalently realized by changing the duty cycle of the sampling structure along the cavity in the middle of which an equivalent phase shift is also inserted. Because the basic grating (seed grating) is uniform, only a common holographic exposure and a µm-level photolithography are required. Therefore, the fabrication cost is highly reduced compared with the true CA grating whose index modulation continuously changes along the cavity. The experimental results show that the laser has good single longitudinal mode operation.

A sub-nanosecond narrow-linewidth pulsed laser source with controllable repetition rate

A compact all-fiber sub-nanosecond narrow-linewidth Yb-doped fiber amplifier with a controllable repetition rate has been investigated. Tunable temporal pulses ranging from sub-nanoseconds to 10 ns with repetition rates from 10 kHz to 1 MHz are obtained by controlling the waveform of the injected electrical-pulse signal. Due to the practical requirements of our intended applications, a distributed feedback semiconductor laser with a wavelength of 1064 nm, pulse duration of 802 ps, repetition rate of 500 kHz and average power of 20 μW is used to seed a dual-stage single mode Yb-doped fiber amplifier. The characteristics of the amplified pulses are measured and exhibit a temporal duration of 810 ps with an average power of 31.2 mW. The gain of the amplified pulse is about 32 dB at the maximum output power. A notable feature of the amplifier pulses is that the spectral linewidth can be maintained to less than 0.1 nm during the dual-stage amplifier process. The noise level lies more than 22 dB below the peak value of the amplified spectrum, which represents an excellent signal-to-noise ratio.

An organic semiconductor laser based on star-shaped truxene-core oligomers for refractive index sensing

The sensing capabilities of an all-organic semiconductor distributed feedback laser based on star-shaped truxene-core molecules are described. Two assays are presented as a proof-of-principle demonstration. In the first, concentration changes in the range of 5–60% (v/v) glycerol solution in water were measured with a bulk detection sensitivity of 21nm per refractive index unit. Secondly, layer-by-layer adsorption of polyelectrolytes to the laser surface, up to a thickness of ≈45nm, was measured. The experimental results from both assays are compared to, and shown to agree with, a theoretical model. Organic semiconductor lasers of this type have a number of attractions including ease of large-scale fabrication, incorporation into existing assay equipment and no rigid optical alignment constraints for excitation and collection of emission, which makes them well-suited to sensing applications. Therefore, it is expected that this technology will be useful in biosensing applications where label-free samples are investigated.

Self-injected semiconductor distributed feedback lasers for frequency chirp stabilization

It is well known that semiconductor distributed feedback lasers (DFB) are key devices for optical communications. However direct modulation applications are limited by the frequency chirp induced by current modulation. We demonstrate that a proper external control laser operation leads to chirp-to-power ratio (CPR) stabilization over a wide range of modulation frequencies as compared to the free-running case. Under experimentally selected optical feedback conditions, the CPR decreases significantly in the adiabatic regime from about 650 MHz/mW in the solitary case down to 65 MHz/mW. Experimental results are also confirmed by numerical investigations based on the transfer matrix method. Simulations point out the possible optimization of the CPR in the adiabatic regime by considering a judicious cavity design in conjunction with a proper external control. These results demonstrate important routes for improving the transmission performance in optical telecommunication systems.

Experimental demonstration of eight-wavelength distributed feedback semiconductor laser array using equivalent phase shift

An eight-wavelength distributed feedback semiconductor laser array with λ/4 equivalent phase shift based on reconstruction-equivalent-chirp technique was demonstrated. It shows very good linearity in lasing wavelengths with its deviation from -0.22 to 0.20 nm. The threshold currents are between 19 and 24 mA. The side-mode suppression ratios are all larger than 40 dB under the bias currents of 70 mA. The slope efficiencies at room temperature are all about 0.4 W/A. The grating was fabricated only by common holographic exposure and an additional micrometer-level conventional photolithography, which results in a low cost.

Experimental Observation of Current-Induced Bistability in a Semiconductor Laser With Positive Optoelectronic Feedback

Bistability in a single-mode distributed feedback semiconductor laser (DFB-SL) with positive optoelectronic feedback (POEF) is observed experimentally. For a given biased current, the output dynamical states of DFB-SL with POEF are critically dependent on variation routes of the laser-biased current. Different routes of biased current variation lead to a bistability characterized by states of different time series, power spectra, and phase portraits.