Other practical types of single frequency laser diodes include dfb lasers and external cavity diode lasers. Single frequency laser diodes like dfb lasers dbr lasers. The closed loop transfer fu nction of such system is. Then the main goal was to control a dfb distributed feedback laser laser with a moderate range of wavelength tuneability by temperature control. Immediately it is obvious that a dfb laser s output is spectrally narrower than its fp counterpart. For a low noise dfb, as shown in figure 3, in the first step the frequency at which the maximum power level appears is obtained from the difference power spectrum as shown in figure 5. Distributed feedback dfb lasers are popular for communications because they have a single longitudinal mode with a very narrow linewidth. Distributed feedback dfb semiconductor lasers emit light in a single mode which is essential to providing the carrier in long haul high bitrate optical communication systems. Here a small signal modulation on the laser current is used to broaden the dfb laser linewidth from a few mhz up to more than 1ghz. Handbook of distributed feedback laser diodes geert. In addition, both conventional and new ways of measuring. High speed directly modulated iiivonsilicon dfb lasers.
A fourth type, the cleavedcoupledcavity laser has not proven to be commercially viable. Highperformance dfb laser module for space applications. Temperature effect towards dfb laser wavelength on. The transfer matrix method tmm is the standard method for simulating resonators with internal reflections occurring in distributed feedback dfb lasers and other laser types. Periodic changes in the laser s refractive index makes it highly reflective at certain. Typical power, voltage and current characteristics of nanoplus 795 nm dfb laser diode if you are uncertain whether you require a dfb laser, compare the specifications with our fabry perot lasers or contact us. One of the ways we help our community of laser scientists and engineers find the best products for their projects is by hosting a free openindex product database. This tutorial will address some of the basics for laser diode handling and operation that should be kept in mind when creating a laser diode system. Dfb laser diode dynamics with optoelectronic feedback 91 where as represents laser transfer function, bs represents feedback loop transfer function, x is the injection current and y is the optical output power. The value of the material gain that satisfies the lasing condition, 2 1 1 2 r r e ag l. The frequency response of the freerunning dfb laser is shown by the black curve, having a freerunning relaxation oscillation frequency of 3 ghz. A1612p dfb laser module the basic laser module, although available as a subcomponent, is usually integrated into a complete transmitter housing such as the fl angemount and plugin packages shown in figure 4.
The structure builds a onedimensional interference grating bragg scattering and the grating provides optical feedback for the laser. Development of semiconductor laser for optical communication. On the various time constants of wavelength changes of a. The simplest way to analyze and understand laser dynamics is using rate equations. Qphotonics offers a variety of single mode fiber pigtailed laser diodes in the wavelength range from 660nm to 1550nm in 14 pin dil, butterfly, mini dil packages. The pro8 provides continuous adjustment of the linewidth over this entire range. White paper laser sources for optical transceivers complete. In recent years the use of diodepumped solidstate dpss lasers in oem applications has been growing rapidly. In the 1990s practical use of wavelength division multiplexing wdm started and pumping lasers for fiber amplifiers and dis tributed feedback dfb lasers were developed for wdm application. The rp photonics buyers guide contains 34 suppliers for distributed feedback lasers. Typical power, voltage and current characteristics of nanoplus 1550 nm dfb laser diode if you are uncertain whether you require a dfb laser, compare the specifications with our fabry perot lasers or contact us.
The dfb laser series of multiquantum well mqw distributed feedback dfb lasers have been designed specifically to satisfy the requirements of sonet cwdm transmission. Single frequency diode lasers are either distributed feedback dfb lasers or distributed bragg reflector dbr lasers. Available wavelengths include 633 nm and the entire range from 760 nm to 3500 nm. Mode hop free tuning of nanoplus 1550 nm dfb laser diode figure 3. A distributed feedback laser dfb is a type of laser diode, quantum cascade laser or optical fiber laser where the active region of the device contains a periodically structured element or diffraction grating. Mode hop free tuning of nanoplus 795 nm dfb laser diode figure 3. Rp photonics encyclopedia distributed feedback lasers. Thus they operate on a single resonator mode emitting quasimonochromatic radiation with a very small linewidth and low phase noise.
Dfb lasers do not use two mirrors to form the optical cavity as used in conventional lasers such as a fp laser. The effects of facet phase on dfb laser spectra are documented and explained. Three laser heads accommodate different diode packages. Periodic structures, like the dbr mirrors in vcsels, can be also realized in a waveguide, as shown below in the case of a ingaaspinp waveguide.
This is a nel nlk1556stb 20mw fiber coupled module in a 14 pin butterfly package with scapc connector. The laser chip is grown by movpe of compound semiconductor material. Peak reflectivity for a particular frequency the bragg frequency via coherent. Laser dynamics singlemode the larger this product the larger is the small signal gain g 0 achievable with a certain laser material. The devices feature high output power and wide operating temperature range.
The bias current was set at 50 ma, and the relaxation oscilla tion frequency fr was 15 ghz in this bias condition. Eindhoven university of technology master design of grating. Attenuation light power propagating in a fiber decays exponentially with length due to absorption and scattering losses. Instead, a diffraction grating is formed on the upper waveguide layer on top of the. Distributed feedback dfb structures and semiconductor dfb lasers. An internal broadband noise source or an internal, freely running, sine wavesquare wave generator is used to modulate the laser current. Tunable semiconductor lasers continue to be in just about everyones list of important components for future fiber optic networks. Apic has developed very low noise rin dfb lasers in the 1550 nm wavelength range with models that perform direct modulation dml up to 6 ghz and continuous wave cw lasers the dml laser come in a variety of optical power outputs from 10 to 40 mw with rin between 160 and 155 dbhz.
In this context, distributed feedback dfb semiconductor laser diodes are widely used in systems as such singlemode laser light sources. Dfb laser diode dynamics with optoelectronic feedback. A restriction of this method is that it cannot be applied to two dimensions or to timedynamic simulations. Examining distributed feedback dfb laser diodes, this title covers the underlying theory, commercial applications, necessary design criteria and future direction of this technology. Long wavelength ingaaspinp distributed feedback lasers. In this chapter, we will setup laser rate equations using the fabryperot optical cavity as a model. Any user of this site is welcome to upload data sheets for products they use and recommend. Tsang etal long wavelength ingaaspinpdfb lasers grown by cbe 35 6 3c z plfrom 6ow cavity 250 m lu dfb laser wafer ascleaved w plfrom 0 1. Relative intensity noise of distributed feedback laser.
This is an especially difficult process when the laser structure utilizes aluminumcontaining layers. Since the emission wavelength of a dfb laser depends heavily on tempera. This longitudinal diffraction grating has periodic. A distributed bragg reflector laser dbr is a type of single frequency laser diode. Fig 1 phase tunable dfb laser with an active dfb qection and a pas sive pc section equations for dfb lasers 1 11, and if the reflections at the laserwaveguide interface are neglected, rr takes the sim ple form trw, n, r2 exp j2k,w, 4 k 2 where r2 is the facet reflectivity at the end of the pc sec. In the second step the respective power level at the obtained frequency is determined from the spectrum with laser on. Modelling the spectra of distributed feedback lasers macsphere. The analogcw lasers have optical power output levels between 40 and 120 mw with rin between 170 to.
Frequency response of a dfb laser at two different bias levels. We started to develop high power pumping laser for fiber am plifier from the early 90s based on the technology devel oped for 1. T o in vestigate the wavelength stability of the laser module, we measured wa velength shifts as a function of the laser cur. Immediately it is obvious that a dfb lasers output is spectrally narrower than its fp counterpart. The lasers can have very lowintensity noise because of the lack of mode partition noise. The distributed feedback dfb laser available in nir and mir incorporates the grating within the laser diode structure itself see figure 2. Lasing will be sustained when the optical gain exceeds the optical losses for a roundtrip in the cavity. A distributed feedback laser dfb is a type of laser diode, quantum cascade laser or optical. B is the bragg wavelength and n eff is the effective refractive index when the lasing mode in the active layer 11. Mode hopping control and lasing wavelength stabilization. Distributed feedback lasers are diode or fiber lasers where the whole laser resonator consists of a periodic structure, in which bragg reflection occurs. Vos, cladiss, philips research eindhoven, updated manual, december.
The authors offer a description of the various effects that determine dfb laser diode behaviour, and also present modelling approaches, describe dfb laser performance aspects, lay out critical guidelines for dfb. Where m is a positive integer that describes the grating order. Figure 2 shows the frequency responses of optical injectionlocked dfb laser across the locking range. At present, however, tuned dfb lasers are expensive because of a bad yield rate. Intended for those interested in understanding omi at a technical level, this whitepaper offers a more indepth look at omi in terms of how it is defined and its importance to optical system performance. Topticas dlc dfb pro lasers integrate both distributedfeedback dfb and distributed bragg reflector dbr lasers. Pdf recent advances in dfb lasers for ultradense wdm. The term laser is an acronym for light amplification by. The threshold current is the current level above which this occurs. Dfb lasers dbr lasers rws lasers single frequency laser diodes have a wavelengthselective grating integrated in the laser chip. These transmitters also may include dc electronics to control the laser temperature and. Digital modulation of a ridgeguide dfb laser at 2 gbits. Free post a pdf data sheet to our openindex product research engine.
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