Dye-Doped Mesostructured Silica as a Distributed Feedback Laser Fabricated by Soft Lithography

We report the laterally tapered ridge waveguide InGaAsP-InGaAsP multiple quantum-well distributed-feedback (DFB) lasers with metal surface gratings, operating at λ ~1.3 μm, by holographic lithography. Single-tapered and double-tapered (bow-tie) ridge waveguide DFB structures with second-order Cr surface gratings are employed to enhance the coupling efficiency. The 600-μm-long laterally coupled DFB laser with a double-tapered ridge waveguide structure exhibits significantly improved single-mode operation without mode hopping, with a maximum sidemode suppression ratio of 42 dB and temperature-dependent wavelength shift up to d λ/dT ~0.071 nm/K.

Uncooled direct modulation of a 1.55 micrometers distributed feedback (DFB) laser is demonstrated at 10 Gbit/s is demonstrated. The small signal performance of the laser at 25 degree(s)C gives rise to a -3 dB bandwidth in excess of 9 GHz, reducing to 8 GHz at 55 degree(s)C. Under uncooled, direct modulation at 10 Gbit/s the back-to-back eye diagrams obtained at temperatures up to 55 degree(s)C are found to be open, with extinction ratios of 6 dB for a peak-to-peak current swing of 40 mA. Transmission at 10 Gbit/s over standard singlemode fiber, is demonstrated over 12 km with the uncooled device. Using this device, multi-level coding is demonstrated at 20 Gb/s, and transmission at 5 Gb/s over 700 m of multi-mode fiber at 60 degree(s)C.

In this paper, we present the theoretical investigation of index-coupled distributed feedback (DFB) laser with tilted single mode ridge waveguides. By tilting part of the ridge waveguide in various degrees, DFB laser with manifold effective grating periods can be realized. The structure is analyzed using couple mode theory in matrix form based on threshold analysis. Important parameters of DFB laser like resonant frequency and threshold gains are obtained by solving the eigen-equation. The results indicate not only that the lasing frequency is modulated by the waveguide titling angle, but also large Gain Margin (GM) can be achieved at the threshold condition which enhance the stable single mode operation in index-coupled DFB laser.

We present a high-power ridge waveguide distributed feedback (DFB) laser with a high-reflective coating and a phase shift section at the rear facet. The phase shift section is realized by means of a micro heater that is placed parallel to the ridge waveguide and the uniform grating. This type of heater section is easy to integrate into existing laser designs and allows adjusting and controlling the spectral behavior of the distributed feedback laser by shifting the rear facet phase condition, which makes it possible to overcome the challenges of mode-hop-free tuning of regular DFB lasers with highly reflective cleaved rear facet. Accordingly, we use the device to quantify rear facet phase conditions where mode hops occur, which are compared to theory with good agreement.

For several fields such as spectroscopy, metrology, and lithography, laser sources in the ultraviolet (UV @ 386 nm) or deep ultraviolet (DUV @ 193 nm) spectral range rely on broad band or pulsed laser systems such as excimer lasers. Highly brilliant semiconductor laser systems could advance these fields further as they are more reliable and easier to handle. One way to achieve the UV emission is using a 772 nm emitting semiconductor master oscillator - power amplifier (MOPA) laser system whose emission is frequency doubled once or twice in a later step. The laser system will be built into a small and compact package and consists of a MO, which is a distributed feedback (DFB) ridge waveguide (RW) laser. The diffraction limited laser emission with a single spectral mode is coupled into the PA for the amplification of the output power up to 3 W. The PA is a semiconductor laser with a RW and a tapered section. Optical feedback can be minimized by using a micro-optical isolator, which is placed between MO and PA that allows a linewidth of We will present further experimental results of the MOPA system in detail. This includes the emission characteristics, the spectral emission behavior, and the robust setup by applying several thermal cycles and shaking tests. On the base of the same laser system, wavelengths of 780 nm or 785 nm could facilitate small rubidium atomic clocks or Raman spectroscopy respectively. Especially when using distributed Bragg reflector laser diodes an even smaller linewidth can be achieved.

By splitting the electrical contact of a conventional distributed feedback (DFB) laser into two sections, the frequency tuning characteristics of the DFB laser are modified and the DFB two-mode degeneracy becomes electrically controllable. As a result, novel device functions can be achieved. Several applications of two-electrode DFB lasers are described: (1) active single-mode stablization, (2) control of spectral reliability and wavelength chirp under amplitude modulation, (3) logic gate operations utilizing the DFB two-mode degeneracy for switching, routing, and optical computing, and (4) frequency modulation of the DFB laser for FSK coherent communication systems and optical sensing.

Distributed feedback (DFB) lasers are used extensively as optical sources within fiber optic telecommunications systems. These semiconductor lasers are valued for their single optical mode operation which enables their use in high bit rate digital and broadband analog transmission systems. We discuss requirements imposed upon DFB lasers used in such applications. We briefly review and illustrate general techniques for modeling DFB laser operation by comparison of measured and modeled device characteristics below and above lasing threshold. We focus on the phenomenon of spatial hole burning which substantially affects operation of all DFB lasers, especially those tailored to produce high fiber coupled power from a single mirror facet. We illustrate insights gained by measurement and modeling of DFB lasers using as an example the particular case of analog transmission of multichannel video signals.

A great improvement in the high-speed characteristics for compressively strained multi-quantum-well (MQW) distributed-feedback (DFB) lasers with self-aligned constricted mesa structures is described. Negative wavelength detuning is an important factor in making possible the extraction of potential advantages for the compressively strained MQW DFB lasers. A 17-GHz bandwidth, which is the highest among the 1.5- mu m MQW DFB lasers, is demonstrated. A wavelength chirp width of 0.42 nm at 10 Gb/s is obtained due to a reduced linewidth enhancement factor that has a magnitude of less than 2. Nonlinear damping K factor in a DFB laser with 45-nm negative detuning has drastically decreased to 0.13 ns, about half of that for unstrained MQW lasers. This is mainly due to an enhanced differential gain as large as 6.9*10/sup -12/ m/sup 3//s. The estimated intrinsic maximum bandwidth is 68 GHz. >

In this paper we present an experimental analysis of the effect of RF modulation injection current in DFB and FP lasers nearthe first period doubling bifurcation (PDB). By increasing the amplitude of the modulation frequency at the onset of PDB thefirst results of a virtual Hopf phenomenon like behavior has been observed in both types of lasers. We characterized thisobservation by increasing the amplitude of the current modulation where two peaks appear in the spectrum, approaching oneto the other until fmally merging the onset of period doubling bifurcation as predicted by theory. The same virtual Hopfbehavior was observed when we set the amplitude modulation at a fixed value and we sweep the frequency modulation at theonset of the PDB point.Keywords: Laser Diode, Nonlinear Dynamics, Period Doubling Bifurcations. 1. INTRODUCTION Nonlinear dynamics in diode lasers has been the subject of many theoretical and experimental investigations in the lastdecade as they show a rich variety of irregular behavior in their route to chaos1. A single frequency diode laser is commonlystudied by a rate equation model which describes the time evolution of the photon and carrier densities. In these equations,the inclusion of an additional degree of freedom as modulation of the injection current, external light injection or opticalfeedback is needed for nonlinear dynamics to appear2.To our knowledge, the nonlinear behavior in semiconductor diode lasers has been extensively studied by many authors usingdelayed optical feedback and strong current modulation. In the former, the observed route to chaos was through successivesubharmonic bifurcations or by quasi periodic route3'4. In the strong current modulation case the period sequence wastruncated by period tripling before the onset of chaos5'6.On the other hand, the onset of a period doubling bifurcation point in many physical systems brings to nonlinear phenomenasuch as: 1) small signal amplification, 2) shift and suppression of the bifurcation point and 3) the emergence of a closelyspaced set of peaks in the frequency response7.In semiconductor lasers the parametric amplification was observed by Harth and co-workers8'9 which was analyzed byWiesenfeld few years after'°. In the study developed by Wiesenfeld in ref. 10, semiconductor lasers were proposed as goodcandidate to study the rich variety of nonlinear phenomena near period doubling bifurcations. A recent study has shown thatthe effect of Langevin noise in period doubling semiconductor lasers has a virtual Hopf ur12 previously predicted byWiesenfeld'34 as a virtual Hopf phenomenon in systems undergoing a period doubling bifurcations in the presence ofexternal noise.In the present study we have experimentally investigated the nonlinear dynamics of diode lasers in the period doublingbifurcation point. We study the influence of the amplitude modulation in Distributed Feedback (DFB) lasers near perioddoubling bifurcations. In Fabry-Perot (FP) lasers we performed as well the same study as DFB lasers and the analysis of thefrequency modulation near period doubling bifurcation. So in section II we described the experimental procedure for theonset of the first period doubling bifurcation performed in commercial DFB and FP InGaAsP diode lasers at 1,3 tm emission

The effects of radiation mode on the oscillating properties of distributed feedback (DFB) lasers with second-order corrugations are analyzed for designing a new type of DFB laser. A formulation based on the transfer matrix technique is applied to calculating Streifer's /spl zeta/-terms added to the coupled-wave equations. These terms represent the effects of radiation and evanescent modes. This formulation greatly simplifies the analysis of distributed resonance along multilayered waveguide structures with arbitrary-shaped second-order corrugations. The effects of vertical resonance are also incorporated into the formulation. Various types of DFB lasers with phase-shifted second-order corrugations are analyzed using this method. It is found that the phase shift and the blaze of the corrugations greatly affect the longitudinal mode selectivity. A new phase-shift DFB laser structure with two complementary blazing regions connected at the shift is proposed. It is demonstrated that this structure has small radiation loss resulting in low-threshold performance despite employing second-order corrugations.

A green‐emitting perovskite first‐order distributed feedback (DFB) laser based on the methylammonium lead bromide (MAPbBr3) with high stability is demonstrated for the first time. The laser achieves stable lasing at 550 nm with a full width at half maximum of 0.4 nm. Low lasing threshold of 60 μJ cm−2 under nanosecond pulsed excitation and 3.1 μJ cm−2 under femtosecond pulsed excitation is observed, showing a much lower lasing threshold compared with the second‐order DFB cavities, which are fabricated on the same substrate. By optimizing the antisolvent treatment and encapsulating with poly(methyl methacrylate), the laser lifetime, resistance to moisture, lasing threshold, and intensity are significantly improved. The lasers are fabricated with a complementary metal‐oxide‐semiconductor‐compatible process, thus offer promising potential for the integrated photonic devices.

We report high slope efficiency and low noise characteristics in a distributed feedback (DFB) laser lasing at 1.3 /spl mu/m with narrow beam divergence by employment of a laterally tapered active stripe over the whole cavity. This tapered structure is designed to realize narrow beam divergence, low threshold current, and high longitudinal mode selectivity. The fabricated tapered-active-stripe DFB lasers demonstrated of 9.20/spl times/13.40 and a record slope efficiency, for a narrow beam DFB laser, of 0.59 mW/mA. The temperature characteristics from -10/spl deg/C to 85/spl deg/C shows high output power at high temperature, stable single longitudinal mode oscillation and stable far-field patterns. Furthermore, for the first time ever, a low relative intensity noise characteristic of under -155 dB/Hz has been realized when butt-coupling into a single-mode fiber.

GaSb-based narrow Ridge Waveguide (RW) laser diodes providing high optical power with low lateral beam divergence single-transverse-mode operation are fabricated and characterized. The typical Separate-Confinement-Heterostructure (SCH) Multi-Quantum-Well (MQW) structure is grown by the solid-state Molecular Beam Epitaxy (MBE). The 1 mm long uncoated RW lasers yield single-transverse-mode output power exceeding 170 mW in the 1950 nm wavelength range under continuous-wave (cw) operation at an injection current of 800 mA and room temperature of 20 ℃. The shallow-etched 7 μm width RW design produces a lateral beam divergence angle as narrow as 9° Full Width at Half Maximum (FWHM) with an excellent beam quality of M²factor < 2 at the maximum output power, enabling it for simple and inexpensive bulk coupling into the typical SM1950 or PM1950 fiber which has a core diameter of 7 μm and numerical aperture (NA) of 0.2. The RW lasers with high output power, good beam quality, and low divergence are promising candidates for a wide range of demanding and advanced applications including pumping fiber amplifiers and solid-state lasers, seeding external cavity lasers, and frequency conversion.

Tunable semiconductor laser has various applications including Wavelength Division Multiplexing (WDM), Frequency Division Multiplexing (FDM), optical switching in Local Area Networks (LAN) and Chemical Sensing, or Spectroscopy. There are different approa ches for tunable semiconductor lasers. Large wavelength tuning range is required for communication applications, such as WDM. Whereas a frequency modulation (FM) requires small but fast frequency shifts. Two-Segmen t laser is one of the methods to realize continuous optical tuning. The device consists of two coupled cav ities having a series of well-defined modes. The modes are equally spaced within a cavity but the mode spacing between the two cavities is slightly different. Characterization results of such lasers are very important. In this paper we will present the characterization results of two segment InGaAs/InP distributed feed back (DFB) tunable lasers. Keywords: DFB Lasers, tunable laser, two segment laser, semiconductor lasers. 1.0 Introduction

Our group has recently demonstrated that a compact master-oscillator power-amplifier semiconductor laser (MOPA-SL) is a good candidate for a coherent light source (operating at 1550 nm) in a Doppler wind Lidar [1]. The MOPA-SL requires two injection currents: I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DFB</inf> for the distributed-feedback (DFB) laser section (master oscillator) and I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">AMP</inf> for the tapered amplifier section. For our laser, the specified maximum current values are 0.7 A and 4.0 A for I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DFB</inf> and I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">AMP</inf> , respectively. Figure 1(a) shows the measurement of CW output power of the MOPA-SL versus I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">AMP</inf> for three different values of I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DFB</inf> = 400, 500, and 600 mA. Our measurements were taken at 19 °C set temperature. The L-I curve shows that the output power linearly increases with IAMP and reaches an ample 1 W level. Although the MOPA-SL has been proven capable of producing single-frequency CW output beam, stable operation at this spectral condition has also been known to highly depend on the drive currents to the laser [2]. It is therefore important to identify pockets of stability in the I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DFB</inf> -I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">AMP</inf> -T <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</inf> (T <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</inf> = laser set temperature) space where lasting single-frequency operation is achieved. At a chosen set temperature Ta <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</inf> = 19 °C, we searched for combinations of (I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DFB</inf> , I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">AMP</inf> ) where the laser operates stably at single-frequency. This was done by observing the spectral characteristic of the laser using an optical spectrum analyzer (OSA, ANDO AQ6315) at different drive current combinations. The resolution of the OSA used is 0.05 nm. Depending on the drive currents, single-frequency or multi-frequency operations of the laser may occur as shown in Fig 1(b). Furthermore, hysteretic mode-hops between single-frequency regimes can occur at higher values of I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">AMP</inf> . When using the laser for a Doppler wind Lidar application, a combination of (I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DFB</inf> , I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">AMP</inf> ) which is close to the center of an identified stable single-frequency regime is used. For the MOPA-SL unit that we use in our Lidar, we typically use (I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DFB</inf> = 0.5 A, I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">AMP</inf> = 3.0 A) at T <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</inf> = 19 °C. These current settings for the laser result in a highly stable Lidar as shown by a 5-day long continuous measurement of the Doppler shift produced by a constantly rotating diffusely reflecting target (Fig. 2).