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Fluorescent proteins have emerged as an attractive gain material for lasers, especially for devices requiring biocompatibility. However, due to their optical properties, integration with distributed feedback (DFB) resonators is not readily achievable. Here, a DFB laser with enhanced green fluorescent protein (eGFP) as the gain material is demonstrated by incorporating a thin (65 nm), high refractive index (n = 2.12) ZrO2 interlayer as waveguide core. Deposition of ZrO2 via atomic layer deposition yields a smooth and conformal film as required to minimize optical losses. Lasing emission is obtained from 2D second‐order DFB eGFP lasers at pump power densities above 56.6 kW cm–2 and a wavelength tuning range of Δλ = 51.7 nm is demonstrated. Furthermore, it is shown that in contrast to conventional organic DFB lasers, both transverse electric (TE) and transverse magnetic (TM) modes are accessible. The effective refractive index of these modes can be predicted accurately through optical modelling. Using far‐field imaging, the laser beam profile is studied and TE and TM modes are distinguished. [ABSTRACT FROM AUTHOR]

Considerable research efforts have been devoted to the investigation of distributed feedback (DFB) organic lasing in photonic crystals in recent decades. It is still a big challenge to realize DFB lasing in complex photonic crystals. This review discusses the recent progress on the DFB organic laser based on one-, two-, and three-dimensional photonic crystals. The photophysics of gain materials and the fabrication of laser cavities are also introduced. At last, future development trends of the lasers are prospected. [ABSTRACT FROM AUTHOR]

The radiation response of distributed feedback (DFB) Bragg gratings written with continuous wave (CW) UV or IR femtosecond lasers in Ge-doped fibers was studied up to the total ionizing dose of 1 kGy(SiO2) since these components are aimed to be used as the laser cavity for space applications. We demonstrated that the ultranarrow passband peaks shift of the same quantity of their Bragg peak since the cavity length cannot change at such low doses. Moreover, the studied DFBs based on type I-UV and type I-IR FBGs show a shift of 5 and 3 pm, respectively, at 1 kGy. These are very encouraging results for their use in real-space applications, but better performances could be obtained by inscribing DFBs based on type II-IR gratings in F-doped fibers since these latter show generally better radiation resistance. [ABSTRACT FROM AUTHOR]

A variety of potential applications such as visible light communications require laser sources with a narrow linewidth and a single wavelength emission in the blue light region. The gallium nitride (GaN)-based distributed feedback laser diode (DFB-LD) is a promising light source that meets these requirements. Here, we present GaN DFB-LDs that share growth and fabrication processes and have surface gratings and sidewall gratings on the same epitaxial substrate, which makes LDs with different structures comparable. By electrical pulse pumping, single-peak emissions at 398.5 and 399.95 nm with a full width at half maximum (FWHM) of 0.32 and 0.23 nm were achieved, respectively. The surface and sidewall gratings were fabricated alongside the p-contact metal stripe by electrical beam lithography and inductively coupled plasma etching. DFB LDs with 2.5 μm ridge width exhibit a smaller FWHM than those with 5 and 10 μm ridge widths, indicating that the narrow ridge width is favorable for the narrowing of the line width of the DFB LD. The slope efficiency of the DFB LD with sidewall gratings is higher than that of surface grating DFB LDs with the same ridge width and period of gratings. Our experiment may provide a reliable and simple approach for optimizing gratings and GaN DFB-LDs.

Since the beginning of the Mars planet exploration, the characterization of carbon dioxide hypersonic flows to simulate a spaceship’s Mars atmosphere entry conditions has been an important issue. We have developed a Tunable Diode Laser Absorption Spectrometer with a new room-temperature operating antimony-based distributed feedback laser (DFB) diode laser to characterize the velocity, the temperature and the density of such flows. This instrument has been tested during two measurement campaigns in a free piston tunnel cold hypersonic facility and in a high enthalpy arc jet wind tunnel. These tests also demonstrate the feasibility of mid-infrared fiber optics coupling of the spectrometer to a wind tunnel for integrated or local flow characterization with an optical probe placed in the flow.

We present the design and the performance of mid-infrared distributed feedback quantum cascade lasers made of strain-balanced GaxIn1-xAs/AlyIn 1-yAs material on InP substrates for wavelength near 5 μm. By changing the grating period within one wafer, we demonstrated wide wavelength coverage of 325 and 282 cm^-1 (16.3% and 14.1% of the center wavelength) under room temperature pulsed and continuous wave (CW) operation, respectively. The variation of pulsed and CW laser performance as a function of wavelength detuning from the gain peak was studied and correlated to the amplified spontaneous emission spectra. We conclude that a slight positive detuning within 5% of the center wavelength favors CW performance especially for high-temperature operation. [ABSTRACT FROM PUBLISHER]

In this paper, we have investigated the mode patterns in real space and reciprocal space, and threshold gain at different band edges in GaN-based photonic crystal surface-emitting lasers (PCSELs) by using the multiple-scattering method. The characteristics at each band edge (\Gamma 1, K2, and M3) of PCSELs are simulated and discussed. In addition, GaN-based PCSELs operated at different band edges have been fabricated and measured. The experimental results of threshold show good agreement with the simulation results. [ABSTRACT FROM PUBLISHER]

We present the design and the performance of mid-infrared distributed feedback (DFB) quantum cascade lasers (QCLs) made of strain balanced \Gax\In1-x\As/\Aly\In1-y\As material on InP substrates for sensing \CO2, \N2O, and NO in the middle wavelength range of mid-IR from 4 to 6 \mu\m. We present the performances of our DFB QCLs at three different aspects: high power, low threshold power consumption, and wide wavelength coverage. We demonstrated a continuous wave (CW) DFB QCL with an output power of 220 mW at 20 ^\circ\C, a CW DFB QCL with low threshold voltage of 8 V and low-divergent far-field angles of 27.5^\circ \times 32.9^\circ by reducing the number of quantum cascaded stages, a CW DFB QCL with a low threshold power consumption of 0.7 W by reducing doping density in the active core, and DFB QCLs wide wavelength coverage of 325 cm ^-1, 16.9% of center wavelength at 5.2 \mu\m, within one wafer by changing the grating period. 12 DFB QCL chips have being aged for 3000 h under 25 ^\circ\C and a constant quasi-CW current of 0.37 A. No decrease in power was observed. [ABSTRACT FROM PUBLISHER]

High-speed 1.3-μm directly modulated lasers (DMLs) have been developed to support sharply rising optical communications traffic. The most crucial requirement for these lasers is the ability to operate over a wide temperature range with no power-consuming electric cooler. Due to poor temperature characteristics resulting from its poor electron confinement in the multiquantum well, DMLs with InGaAsP material systems have been replaced by DMLs with InGaAlAs material systems, which have stronger electron confinement. In this paper, progress in uncooled 25-Gb/s 1.3-μm InGaAlAs DMLs is summarized. A 160-μm-long ridge-waveguide-type laser showed a lower threshold current Ith of 14.9 mA at high temperatures up to 95 °C, and a small signal-frequency-response bandwidth f3dB of 14 GHz was achieved at a bias current of 60 mA at 95 °C. Using this laser, clear 25-Gb/s operation was obtained at 95 °C. In addition, stable operation was achieved for up to 4000 h at 85 °C, indicating the basic applicability of the device to next-generation 25-Gb/s data communication systems. Furthermore, the developed technology was applied to a novel uncooled 25-Gb/s 1.3-μm surface-emitting laser for optical interconnects, in which a 45° mirror and a lens were integrated monolithically. [ABSTRACT FROM PUBLISHER]

A distributed feedback (DFB) semiconductor laser with three phase shifts based on reconstruction equivalent chirp (REC) technology is proposed and investigated numerically. With the combination of multiple phase shifts and corrugation pitch modulated (CPM) structure, we also propose a novel and more complex structure named dual CPM, which has a flatter light power distribution along the laser cavity compared with the true double phase shifts DFB laser diode (LD), while the P-I curves are nearly the same. The proposed dual CPM structure is also designed and analyzed based on REC technology. The simulation results show that, the DFB semiconductor laser with complex structure such as phase shifts, or even arbitrary variation of the grating period can be achieved equivalently and easily by changing the sampling structure. But its external characteristics are almost the same as those DFB lasers with true phase shifts, or true arbitrary variation of the grating period. The key advantage of the REC technology is that it varies only the sampling structure and keeps the seed grating (actual grating in sampling structure) period constant. So its fabrication needs only low-cost and standard holographic exposure technology. Therefore we believe this method can achieve the high-end and low-cost DFB LD for mass production. [ABSTRACT FROM AUTHOR]

Since the beginning of the Mars planet exploration, the characterization of carbon dioxide hypersonic flows to simulate a spaceship's Mars atmosphere entry conditions has been an important issue. We have developed a Tunable Diode Laser Absorption Spectrometer with a new room-temperature operating antimony-based distributed feedback laser (DFB) diode laser to characterize the velocity, the temperature and the density of such flows. This instrument has been tested during two measurement campaigns in a free piston tunnel cold hypersonic facility and in a high enthalpy arc jet wind tunnel. These tests also demonstrate the feasibility of mid-infrared fiber optics coupling of the spectrometer to a wind tunnel for integrated or local flow characterization with an optical probe placed in the flow. [ABSTRACT FROM AUTHOR]

Deriving a dynamic model based on the coupled-mode and carrier rate equations, the effects of coupling coefficient and corrugation position on all-optical flip-flops (AOFF) we have analyzed in this paper. Also the self phase modulation (SPM) in the distributed coupling coefficient distributed feedback semiconductor optical amplifier (DCC-DFB-SOA) has been implemented. Then the effects of SPM on the rise and fall times of the flip-flop DFB-SOA are investigated. It has been shown that the application of the optimized coupling coefficient and corrugation position improves the speed limitation in AOFF significantly. The transfer matrix method (TMM) time domain is utilized for the numerical simulations. [ABSTRACT FROM AUTHOR]

Expertise of packaging for optoelectronic components requires the solution of optical, mechanical, and electrical problems in the same way. The purpose of this paper is to present three-dimensional simulations using finite-element method (FEM) of thermomechanical stresses and strains in 1550-nm laser modules induced by Nd:YAG crystal laser welds and thermal cycles on main subassembly laser submount. Nonlinear FEM computations, taking into account of experimental σ(ε) measured curves, show that thew laser welding process can induce high level of strains in columns of the laser platform, bearing the laser diode, responsible of an optical axis shift and a gradual drop of the optical power in relation with relaxation of accumulated stresses in the subassembly (W. M. Sherry et al., "High performance optoelectronic packaging for 2.5 and 10 Gb/s laser modules," in Proc. Electron. Compon. Technol. Conf., 1996, pp. 620-627). Typical stresses are close to 160 MPa with drift about 5 MPa with the dispersion of energy level of the laser Nd: YAG beam. The introduction of both material and process dispersion in order to evaluate their impact on product lifetime distribution has been taking into account. In the case of thermal cycles, stresses can occur on elements sensitive to coefficient of thermal expansion mismatches such as solder joints between the laser platform and thermoelectric cooler and as fiber glued into the pigtail leading to crack propagation with sudden drop of optical power. A previous paper demonstrated that laser submount is the most sensitive part of optical system (Deshayes, et al., "Three-dimensional FEM simulations of thermal mechanical stresses in 1.55 μm laser modules," Microelectron. Rel., vol. 43, no. 7, pp. 1125-1136, Jul. 2003). Experimental analyses were also conducted to correlate simulation results and monitor the output optical power of laser modules after 500 thermal cycles (-40 °C/ + 85°C VRT). [ABSTRACT FROM AUTHOR]

A heterogeneous high-performance quantum-cascade laser gain chip comprising two bound-to-continuum active region designs emitting at 8.2 and 9.3 μm is presented. Its extrapolated gain spectrum has a full-width at half-maximum (FWHM) of 350 cm-1. Though a broad gain bandwidth invariably results in a reduced gain cross section, devices with a high-reflection coated back facet still lase continuous-wave (CW) up to a temperature of 50°C and demonstrates output powers in excess of 100 mW at 30°C. Such high performance was achieved by designing the wave- guide in a buried heterostructure fashion and epi-down mounting on a diamond submount, resulting in a thermal resistance of only 4.8 K/W. In pulsed mode, we reached a peak output power of 1 W at room temperature. Finally, in order to prove the usability for broad-band tuning, this chip was antireflection coated on the front facet with a residual reflectivity of < 2.5 x 10-3 and used in our external cavity (EC) setup operated at room temperature. In pulsed mode, we were able to tune the gain chip over 292 cm-1, which is 25% of center frequency. In CW, we reached a coarse tuning range of 201 cm-1 (18%) and an output power in excess of 135 mW at the gain maximum at 15° C. This gain chip enabled CW room temperature EC tuning with output powers in excess of 20 mW over 172 cm-1. [ABSTRACT FROM AUTHOR]

A standing-wave model based on "cold" cavity mode expansion is proposed and presented for simulation of distributed feedback (DFB) semiconductor lasers. The model is validated against the well-established traveling-wave model in terms of the static and dynamic characteristics of typical DFB lasers. Effects such as the longitudinal variation of carrier and photon densities and nonlinear gain saturation, known as the spatial and spectral hole burning, respectively, are all included in this model. Simulation examples show that the proposed approach is computationally more efficient than the traveling-wave model. The impact of the expansion mode truncation on the accuracy and efficiency is also investigated and discussed. [ABSTRACT FROM AUTHOR]

A systematic investigation of gain-clamped semiconductor optical amplifiers (GC-SOAs) based on the second-order index-coupled DFB gratings is carried out by way of simulation. In particular, we focus on the main effects of the radiation loss caused by the first-order diffraction of the gratings on the amplifier performance. The magnitude of the total complex coupling coefficient is the main factor to determine the level of gain clamping. We demonstrate that a high-performance GC-SOA can be realized by using purely loss-coupled second-order DFB gratings with more relaxed tolerance on grating strength and period. It is shown that, in the presence of weak reflection-related coupling, the parasitic radiation loss associated with the second-order grating always helps to expand the linear amplification region and to reduce the longitudinal spatial hole burning along the cavity. Further, we demonstrate through comparison that the GC-SOAs have higher saturation power and much shorter carrier lifetime than the conventional SOAs. An improved design by longitudinal variation of the grating duty cycle is proposed such that the noise performance of the amplifier can be enhanced without much sacrifice on the linear amplification regime. [ABSTRACT FROM AUTHOR]

The power spectral density of the optical intensity in RF modulated optical links is investigated theoretically and experimentally in interferometric systems with a good agreement. The influence of the Henry factor a of directly modulated distributed feedback laser diodes is shown on the conversion of phase noise into intensity noise for the first time. [ABSTRACT FROM AUTHOR]

The use of optoelectronic integrated circuits (OEICs) is now emerging as a practical technology for a variety of applications, particularly in advanced telecommunications. OEICs consist of a range of devices such as lasers, waveguides, modulators, amplifiers, transistors, detectors, etc. fabricated on the same substrate. When a semi-insulating substrate is used, these devices can be electrically isolated by channel etching, resulting in a low capacitance structure with reduced electrical interference between the subcomponents. One of the devices which is particularly advantageous for this type of integration scheme is the distributed feedback (DFB) laser. The laser can be made to function more efficiently by minimizing the current flowing outside the active region. This can be achieved by surrounding the active region with semi-insulating iron doped InP. This work describes for the first time, the MOVPE growth, fabrication, and device characterization of 1.3 um buried heterostructure DFB MQW lasers, which combine the advantages of using both a semi-insulating substrate and a semi-insulating infill region in the same device structure. The potential advantage of this design scheme is improved OEIC performance as a result of, reduced capacitance and electrical crosstalk, enhanced laser output power, higher speed, increased efficiency, wider operating temperature and reduced threshold current. The laser active region consists of 8 x 140 Å quantum wells of GalnAsP (λ = 1.3 μm) and 110 Åbarriers of GalnAsP (λ= 1.07 μm). Single mode 1.3 urn devices of length 250 μm operating at room temperature produced threshold currents of 8 mA, efficiencies of up to 25%, output powers of 18 mW at 80 mA (pulsed), and a frequency response greater than 12GHz. The parasitic capacitance was estimated to be less than 3 pF. [ABSTRACT FROM AUTHOR]

High-power broad area substrate-emitting distributed feedback (DFB) quantum cascade laser emitting at λ ~ 4.6 μm is reported. Proper second-order DFB grating coupling, low waveguide loss mechanism, and epilayer-down mounting bring about a high vertical radiative optical power. The maximum peak power is as high as 1.82 W at 20 °C and still 1.22 W at 50 °C operated in pulsed mode with a pulsed width of 1 μs and duty cycle of 0.2%. A single-lobed radiation far-field with a divergence angle of 7.9 ° in the ridge-width direction and two-lobed radiation far-field with a divergence angle of 0.61 ° in the cavity-length direction are achieved by depositing the high-reflection coatings on both facets. Robust single-mode emission is continuously tunable by the heat sink temperature up to 115 °C. [ABSTRACT FROM PUBLISHER]

A novel tunable 1550-nm buried heterostructure (BH-) distributed feedback (DFB)-laser is presented consisting of a phase tuning section, a short cavity complex coupled DFB section, and an amplifier section with integrated optical taper. The device shows a narrow optical far-field, a high optical output power, up to 10-Gb/s direct modulation capability and a wavelength tuning range of several nanometers by varying the current in the phase section only. [ABSTRACT FROM PUBLISHER]

An athermal operation of the lasing wavelength in a membrane buried heterostructure distributed feedback (BH-DFB) laser was demonstrated by adopting a polymer (benzocyclobutene) cladding layer which has a negative temperature coefficient of refractive index. Membrane BH-DFB lasers of core thickness 65 nm were operated under room-temperature continuous-wave conditions. The temperature dependence of the lasing wavelength was measured to be 2.45times10-2 nm/degC, which is about 20%-30% of that for conventional semiconductor lasers [ABSTRACT FROM PUBLISHER]

A novel structure for dual-wavelength distributed feedback (DFB) fiber laser is proposed and experimentally demonstrated. This structure is based on a uniform fiber Bragg grating with two unequalized phase shifts, which markedly suppress the mode competition of the two lasing wavelengths; and then a 52-pm-spaced dual-wavelength DFB fiber laser operating at single-longitudinal-mode and single-polarization is achieved at room temperature. A simple method is also implemented to fabricate the phase shifts with high precision [ABSTRACT FROM PUBLISHER]

A chirped phase-shifted structure is demonstrated for compact multiwavelength distributed feedback (DFB) fiber laser at room temperature for the first time. The chirped structure provides separated resonance cavities and then the stable multiwavelength operation. The equivalent phase shift method is demonstrated to realize the desired chirp and phase shifts simply and flexibly. A 44-pm-spaced dual-wavelength DFB fiber laser is then achieved experimentally, which is the narrowest spacing ever reported for a compact multiwavelength fiber laser [ABSTRACT FROM PUBLISHER]

The InAs-InAlGaAs quantum dot (QD) lasers with the InAlGaAs-InAlAs material system were fabricated on distributed feedback (DFB) grating structures on InP (001). The single-mode operation of InAs-InAlGaAs QD DFB lasers in continuous-wave mode was successfully achieved at the emission wavelength of 1.564 mum at room temperature. This is the first observation on the InP-based QD lasers operating around the emission wavelength window of 1.55 mum. The threshold current density of the InAs-InAlGaAs QD DFB laser with a cavity length of 1 mm and a ridge width of 3 mum, in which one of the cleaved facets was coated with 95% high-reflection, was 1.23 kA/cm2 (176 A/cm2 for single QD layer). The sidemode suppression ratio value of the QD DFB laser was as high as 42 dB at the driving current of 100 mA [ABSTRACT FROM PUBLISHER]

Monolithic widely tunable laser diodes commonly employ sophisticated grating structures to achieve wide wavelength tuning by exploiting the Vernier effect. The reflection spectra of these gratings are, however, susceptible to any unintended reflections, which cause interference effects and impair the tuning behavior of the laser. The main source of such reflections are the front and rear facet of the device. Their influence on the tuning characteristic is significant and will be discussed in this letter. Furthermore, a statistical yield analysis is presented, which relates device yield to important design parameters. [ABSTRACT FROM PUBLISHER]

Device and tuning characteristics of sampled grating tunable twin-guide laser diodes are presented. The vertically integrated, monolithic widely tunable laser requires only two tuning currents to fully cover a wavelength range of more than 40 nm by electrooptic tuning. Its tuning behavior is quasi-continuous with up to 8.2-nm broad continuous tuning regions. High sidemode suppression (SMSR ≥ 35 dB) as well as large output power (P ≥ 10 mW) are obtained over the wavelength range from 1520.5 to 1561.5 nm. [ABSTRACT FROM PUBLISHER]