Tuning range and spectral selectivity of the distributed forwardcoupled (DFC) laser

The tuning performance and spectral filtering mechanism in the distributed forward-coupled (DFC) laser diode are investigated. This widely tunable device is based on codirectional mode coupling along the entire laser length by a gain/loss grating perturbation. Due to the transverse integration, even rather short (L≈300-600 μm) DFC lasers may achieve side-mode suppression superior to that of previous codirectionally coupled devices over similar tuning ranges. Model calculations yield a tuning range above 100 nm at 1.5-μm wavelength with a side-mode suppression ratio around 30 dB     

Wide wavelength tuning of sampled grating tunable twin-guide laser diodes

Tuning characteristics of widely tunable twin-guide (TTG) laser diodes with sampled gratings (SGs) are reported. Two SGs, providing slightly different reflection spectra, enable wide tunability by means of Vernier effect tuning. The device structure is vertically integrated and, hence, a DFB-like laser is obtained, which makes a phase tuning section unnecessary and facilitates easy and fast device characterisation. Although the tuning section can tune the SG reflection spectra by only /spl sim/2 nm, an overall tuning range of 28 nm has been achieved by employing Vernier effect tuning. Within the aforementioned tuning range, five supermodes are usable and can be tuned continuously without any mode-hops. The lasers operate at /spl sim/1.55 /spl mu/m wavelength and achieve a maximum output power of 12 mW.     

Reflection-induced changes in the optical spectra of 980-nm QWlasers

High-power 980-nm strained quantum well diode lasers having low reflectivity facet coatings are sensitive to weak reflections that affect the laser emission spectrum. In devices having 0.2% output facet reflectivity, 2% reflections from an external plane mirror shifted the output spectrum from 970 to 1000 mn. Wavelength stabilization and improved immunity to spurious reflections were demonstrated using bulk grating and fiber-grating reflectors. Continuous laser tuning from 958 to 1011 nm was achieved with 1% net grating reflectivity     

高功率激光辐射近场鬼点反射对激光器损伤及抑制方法研究

高功率固体激光系统中的光学透镜对激光束的残余反射,可形成能量较大的鬼光束,极易对元器件及激光器造成损害,研究了高功率激光装置中的鬼点反射及其带来的破坏影响,给出了避开鬼点反射损伤的方法,可为高功率激光装置中透镜的设计提供参考．     

Two-electrode DFB laser filter used as a wide tunable narrow-bandFM receiver: tuning analysis, characteristics and experimental FSK-WDMsystem

Characteristics of a two-electrode DFB laser filter are studied both theoretically and experimentally. Using a matrix analysis of spontaneous emission, a continuous tuning range of 6.7 Å is achieved by changing both net field gains of the two electrodes. A total discontinuous tuning range of over 10 nm comprising alternating mode jumps and continuous tuning range of 4 Å are measured experimentally. The laser filter presents a FWHM bandwidth of 5 GHz which depends on the optical input power. In addition, it is demonstrated that a DFB laser filter can act as a frequency discriminator/photodetector, i.e., a narrow-band FM receiver, with a uniform bandwidth of 1.5 GHz. Using the two-electrode DFB laser for both transmitter and receiver, a two-channel FSK-WDM transmission system utilizing the discontinuous tuning range is reported. The advantage of such a device is the simplicity as compared to the heterodyne technique     

Quasicontinuous wavelength tuning in super-structure-grating (SSG)DBR lasers

The paper describes the design of a super-structure-grating distributed Bragg reflector (SSG-DBR) laser for broad quasicontinuous wavelength tuning with stable single-mode operation. The phase distributions and the effective coupling coefficients of SSG's are optimized to obtain both broad tuning range and high mode selectivity. A computer-aided simulation of wavelength tuning, where the effects of the waveguide loss increase and inhomogeneous gain spectrum are included, provides an optimum cavity structure and indicates the possibility of more than 70 mm quasicontinuous tuning in a 1.55 μm InGaAsP-InP SSG-DBR laser. Experimental results for 34 nm quasicontinuous tuning with a properly designed device are also presented     

Tuning performance and spectral selectivity of widely tunablevertical Mach-Zehnder lasers

The filtering mechanism, spectral selectivity, and tuning performance of the vertical Mach-Zehnder (VMZ) laser diode are studied. Wavelength selection in this device is due to the interference of two modes with different and electronically controllable optical path lengths in analogy to a common Mach-Zehnder interferometer. Different design approaches for the VMZ laser are investigated. The calculations presented show that tuning ranges between 50 nm and 100 nm with side-mode suppression ratios (SSR's) of more than 20 dB are feasible. Designs with tuning ranges of about 35 nm show SSR values of over 30 dB at the 1.55 μm wavelength enabling the realization of widely tunable laser diodes with full wavelength access within the tuning range, suitable for applications in optical communication systems     

Tunable polymer double micro-ring filters

Based on the vernier effect, widely tunable polymer double micro-ring filters using the thermooptic effect or the electrooptic effect are demonstrated. A tuning enhancement factor of 40 was achieved at wavelengths near 1550 nm. The tuning rate for the thermooptic device is 120 GHz/mW and for the electrooptic device is 120 GHz/12 V. A tunable laser with a side-mode suppression ratio greater than 30 dB was demonstrated using this filter and erbium-doped fiber amplifier gain. Thermal tuning over 35 nm was achieved.     

Modeling self-pulsating DFB lasers with an integrated phase tuningsection

A theoretical model of a self-pulsating three-section DFB laser with an integrated phase tuning section is established. It is based on traveling wave equations and the standard carrier rate equations. Parameters of an existing device are used for applying the model. Key conditions and characteristics of self-pulsations (SPs) are modeled and compared with experimental results. The important role of phase tuning for turning on the SP is pointed out. The dependence of the SP regime on the detuning between the Bragg wavelengths in the laser and reflector is determined and the essential role of phase-readjustment is identified. Frequency tuning via the laser currents, as well as the pulse shape at various frequencies, is investigated. This allows us to identify the mechanism for frequency tuning. The model turns out to be a good tool to improve our knowledge of the self-pulsation effect and to design optimized devices     

The Match Checker---A Simple Instrument for Matching Impedances in Waveguide and Coaxial Systems (Short Papers)

The match checker is a self-contained passive device, which, when inserted between ports of a waveguide or coaxial-line system, provides an indication of the mismatch at each port. It does not require tuning, and internal reflections from components of the match checker do not limit the accuracy of the match which may be obtained. It is therefore suitable for use in matching ports with the high precision needed for calibration systems.     

Micromirror device controlled tunable diode laser diode laser

An electronically controlled external cavity laser diode for fast wavelength tuning and multiple-colour lasing is presented. The spectral-tuning is accomplished by a digital micromirror device. Tuning of 47.4 nm with a tuning speed of 0.85 nm/ms was achieved. Simultaneous emission of up to 9 laser lines is demonstrated     

Codirectionally coupled twin-guide laser diode for broadband electronic wavelength tuning

A novel broadband tunable laser diode is presented. It is based on a codirectional coupling scheme which is predicted to yield tuning ranges larger than 50 nm. Only a single control current is required for tuning. Preliminary devices have been realised indicating a wavelength tuning over 30 nm.<>     

DFB laser with attached external intensity modulator

A theoretical study is made of the frequency pulling effect exerted on a distributed feedback (DFB) laser by an external amplitude modulator that is directly attached to it. The modulator consists of a piece of waveguide whose loss is modulated by means of an externally applied voltage. The modulator affects the laser due to residual reflections from its far end which appear as a variable effective reflectivity to the output end of the DFB laser. Modulation affects the magnitude as well as the phase of the effective reflection coefficient presented to the laser due to the coupling of the real and imaginary parts of the effective refractive index of the modulator waveguide. The tuning problem is formulated as an eigenvalue equation for the DFB laser in the presence of an externally attached lossy cavity     

1.5 μm phase-controlled distributed feedback wavelength tunableoptical filter

A 1.5-μm phase-controlled distributed feedback wavelength-tunable optical filter is studied. This is the first optical filter which controls the transmissivity (gain) and the transmission wavelength independently. Wavelength tuning range as wide as 43 GHz (3.4 Å) with high constant gain of 27 dB has been achieved. A five-channel wavelength selection with less than -10 dB crosstalk is expected with this filter. This device also operates as a wavelength tunable laser, and the wavelength tuning range as a laser is larger than as a filter. The reason is studied, and it is shown that suppression of the submodes is important to expand the wavelength tuning range     

Theoretical characteristics of a tunable two-electrode Fabry-Perot(TEFP) laser diode

The theoretical tuning characteristics of a two-electrode Fabry-Perot (TEFP) laser diode are derived using a relative simple model. This type of laser can be used as a tunable source. Tuning can be achieved by driving the device along a constant-power contour while the wavelength changes during the travel of the operating point. The characteristics indicate constant-power FM and constant-wavelength AM operating modes for the TEFP device. The laser exhibits ability similar to that of a multielectrode distributed-feedback or distributed-Bragg-reflector laser     

Continuously tunable organic solid-state DFB laser utilizing molecular reorientation in molecular glasses

We report a facile way for continuously tuning the lasing wavelength of an organic thin-film distributed feedback (DFB) laser after device fabrication by varying the effective refractive index seen by the one-dimension DFB laser structure. Varying the effective refractive indices of the organic gain medium and thus the effective refractive index of a one-dimension DFB laser structure after device fabrication is made possible with reorientation of molecules in a molecular glass at elevated temperatures. Distributions of molecular orientations can be fine controlled by annealing temperatures and times, permitting continuous tuning of optical properties and lasing wavelengths. Molecular reorientation can be conducted after devices are made, thus giving one the freedom to set or tune the lasing wavelength to meet a particular purpose with a common structure.     

External-cavity semiconductor laser with 1000 GHz continuouspiezoelectric tuning range

A 1000-GHz continuous tuning range is achieved using a single piezoelectric transducer to orient a diffraction grating in an external-cavity semiconductor laser. The laser output power ripple versus wavelength is 15%, and the linewidth is less than 500 kHz. Large-amplitude piezoelectrically controlled wavelength modulation can be done at modulation frequencies on the order of 100 Hz. The maximum modulation frequency, continuous electrical tuning range, and linewidth are limited by the mechanical design of the external cavity. This device should have wide application in spectroscopy, metrology, and remote sensing     

SGDBR激光器中取样光栅的理论和实验研究

讨论了取样光栅分布布拉格反射激光器(SGDBR)中取样光栅对激光器调谐范围、输出功率和光谱质量的影响,介绍了其设计流程,并据此对SGDBR进行了实验研究.其取样光栅的反射谱和设计相符,且在30nm准连续调谐范围内边模抑制比都大于30dB.     

Tunable dual-mode operation in a chirped gratingdistributed-feedback laser

We report on the tunable dual-mode operation of a chirped grating distributed-feedback (DFB) laser device with two integrated modulators which act as tuning sections. A transfer-matrix model is used to simulate the amplified spontaneous emission spectrum for a chirped grating DFB laser. Several types of dual-mode operation are observed for wavelength spacings of 0.5 nm and 1.4 nm corresponding to frequency detunings of 63 GHz and 175 GHz     

High-speed direct Modulation of widely tunable MG-Y laser

The dynamic performance of the modulated-grating Y-branch laser is presented. In order to reach over 40-nm tuning range, the devices utilize an additive Vernier effect and relative tuning of two reflecting gratings. The device shows high (>13 dBm ex-facet) and uniform (<1.2-dB variation) steady state output power over the tuning range, and sidemode suppression ratio >40 dB. The laser behavior under small- and large-signal operation conditions is investigated. The laser exhibits a resonance frequency of 7.4-8.8 GHz at 80-mA bias. A 10-Gb/s eye diagram measurement showed high extinction ratio and signal-to-noise ratio.