At injection levels i below threshold i linewidth enhancement fador in single quantumwell grinsch semiconductor lasers is investigated theoretidy and experimentally. This paper investigates the dynamical and nonlinear properties of silicon based qd lasers through the prism of the linewidth broadening factor i. Thermally insensitive determination of the linewidth. Developments of narrowlinewidth distributedbraggreflection dbr and distributedfeedback dfb lasers are described. Jun 15, 2016 thermally insensitive determination of the linewidth broadening factor in nanostructured semiconductor lasers using optical injection locking. Quantum cascade laser, linewidth enhancement factor, optical. The consequences for the linewidth and transient wavelength chirping in 1. This value is 30 times greater than can be explained by existing theories. The measured linewidth broadening factor is in good agreement with theoretical calculations that include the most important many. The linewidth broadening factor of semiconductor lasers, which is also known as. Results for two lasers at 7 nm and 20 nm detuning from the gain peak will be presented to compare the effects of minimizing the linewidth enhancement factor, figure 4 shows the power dependence of the electrical power spectrum fwhm of the lasers using a 5km fiber.
To test whether this acoustic broadening was from the measurement system or from the test laser, the entire 11 km fiber length was placed in a styrofoam box to isolate it from these acoustic noises. The linewidth enhancement factor, also known as the. The semiconductor diode laser sl has a number of properties that make it a desirable. An improved delayed selfheterodyne interferometer for. Roundrobin measurements of linewidth enhancement factor. The linewidth enhancement factors have a very modest effect on pulse energy for a given current and absorption, but a more noticeable one on amplitude and duration. Moloneyl 1 arizona center for mathematical sciences, university of arizona, tucson az 85721, usa 2 us.
A theoretical analysis for gigabitsecond pulse code modulation of semiconductor. In quantum cascade lasers, since the lasing transition occurs between two subbands of the conduction band that have therefore similar curvatures, the linewidth enhancement factor was expected to be naught. Pdf chapter 4 determination of linewidth enhancement. The emission linewidth above threshold is measured in a gaasalgaas microcavity surface. The objective of this paper is to present an overview of topics related to one of the fundamental parameters for semiconductor lasersthe linewidth broadening factor. Linewidth enhancement factor 1, also know as chirp parameter or. The linewidth of qd dfbs with different gain offsets and a commercial 1. One property that distinguishes semiconductor lasers from most other laser systems is that there is a strong. A new method for measuring the linewidth enhancement factor. Pdf linewidth broadening factor of an interband cascade. The design of a narrowlinewidth dbr laser is described in detail.
Forthe latter, a dependence ofthe ccfactor onthe injected current is observed, and the experimental results are compared with numerical simulations based on a keldysh nonequilibrium greens functions approach. Intrinsic homogeneous linewidth and broadening mechanisms. Osa linewidth enhancement factor in semiconductor lasers. Semiconductor quantum dot lasers epitaxially grown on. On the other hand, the laser linewidth from stabilized lowpower continuouswave lasers can be very narrow and reach down to less than 1 khz. Simple method for measuring the linewidth enhancement factor of semiconductor lasers abstract a simple method for measuring the linewidth enhancement factor lef of semiconductor lasers sls is proposed and demonstrated in this paper. Forthe latter, a dependence ofthe cc factor onthe injected current is observed, and the experimental results are compared with numerical simulations based on a keldysh nonequilibrium greens functions approach. Buus, linewidth broadening factor in semiconductor lasersan overview, ieee j. The gain offset is defined as the difference between the dfb wavelength and the gain.
The semiconductor diode laser sl has a number of properties that make it a desirable light source for spectroscopy. The factor 12 serves to convert the change of power gain. Linewidth broadening factor and optical feedback sensitivity. Theory of the linewidth of semiconductor lasers ieee. Fm is the fm efficiency mhzma, i b is the bias current level above threshold, and. Linewidth broadening due to longitudinal spatial hole. This work reports the linewidth broadening factor lbf of a continuouswave interband cascade laser operated both below and above threshold. We also need expressions for the light coming out of the laser. This work reports on the ultralow linewidth enhancement factor a hfactor of semiconductor quantum dot lasers epitaxially grown on silicon. The design of a narrow linewidth dbr laser is described in detail. A novel method for extracting the linewidth broadening. For thin wells a small linewidth enhancement factor is obtained which clamps with increasing carrier density, in contrast to the monotonous increase observed for thicker wells. Buus, linewidth broadening factor in semiconductor lasers an overview, ieee j. Oct 29, 2019 this work reports the linewidth broadening factor lbf of a continuouswave interband cascade laser operated both below and above threshold.
Laser linewidth theory was pioneered by schawlow and townes 1 and further developed in 2 and 3. We show that for a dfb laser without facet reflectivity, the reduction of the linewidth with the laser length will be slower than 1 l 3 due to longitudinal spatial hole burning. The simulation results show that the powerlinewidth product can increase by a factor greater than 2 due to lshb for long dfb lasers. The gain and absorber linewidth enhancement factors. Dynamics and spectral characteristics of quantum dot. Linewidth broadening factor in semiconductor lasers ieee xplore. Air force phillips lab, kirtland afb, nm 87117, usa 3 permanent address. Linewidth broadening factor of a microcavity semiconductor.
The value of lef is very important for many aspects of laser. We discuss the status of the schawlowtowneslaxhenry stlh theory of laser linewidth in the instance of semiconductor injection lasers. Linewidth broadening factor and gain compression in. Using the hakkipaoli method, the belowthreshold lbfs around the gain peak are determined to be in the range of 1. In addition, low chirp attributes to small linewidth enhancement factor lef which is an essential parameter in semiconductor lasers and determines the modulationinduced chirp, spectral linewidth, external optical injection sensitivity, and output beam characteristics 9, 15. Introduction the most important property of lasers not captured by semiclassical theories, which treat the. Semiconductor lasers are very different from other lasers because refraction variation cant be avoided when the gain is changed. Rp photonics encyclopedia linewidth, bandwidth, laser. Indexing terms measurement, semiconductor lasers a simple and accurate method to measure the linewidth enhancement factor u in dfb semiconductor lasers is pro posed.
This method is based on the selfmixing effect when a small portion. In semiconductor lasers, spontaneous emission events affect carrie r density, resulting in refractive index and phase changes, thus broadening the linewidth 29. Bhattacharyya, role of linewidth enhancement factor on the frequency response of the synchronized quantum cascade laser, opt. Linewidth broadening factor of an interband cascade laser. Only the photons that leave the cavity from the mirrors constitute useful output. There was no ob served decrease in the laser linewidth due to this system. Novel measurement technique of alpha factor in dfb. Clamping of the linewidth enhancement factor in narrow quantumwell grinsch semiconductor lasers j. We also discuss the various factors influencing the linewidth in microcavity and strained quantum well lasers and the relation between lasing threshold. Thermally insensitive determination of the linewidth broadening factor in nanostructured semiconductor lasers using optical injection locking. Rp photonics encyclopedia linewidth enhancement factor.
This parameter is called linewidth enhancement factor lef. The analysis of different material demonstrates that the. Buus, linewidth broadening factor in semiconductorlasers an overview, ieee j. Roundrobin measurements of linewidth enhancement factor of. Mar 01, 2019 this paper investigates the dynamical and nonlinear properties of silicon based qd lasers through the prism of the linewidth broadening factor i. Linewidth broadening factor in semiconductor lasersan. Using the hakkipaoli method, the belowthreshold lbfs.
The parameter that quantifies the magnitude of this effect is the linewidth broadening factor lbf, also known as. Although this formula predicts the linewidth satisfactorily for gas lasers, it fails to predict the linewidth for semiconductor lasers. Oka mura and iwatsuki 3 used a dhsi system with a 72 km fiber delay line to measure the linewidth of an erbium. Dynamic line broadening of semiconductor lasers modulated at. Intrinsic homogeneous linewidth and broadening mechanisms of. The objective of this paper is to present an overview of topics related to one of the fundamental parameters for semiconductor lasers the linewidth broadening factor.
A firstorder frequencydependent formula of the linewidth broadening factor. Semiconductor lasers are the most notable of these. Cthk1 linewidth enhancement factor of semiconductor. We also discuss the various factors influencing the linewidth in microcavity and strained quantum well lasers. Refraction variation can be introduced the theory of semiconductor laser by a dimensional parameter. Cthk1 linewidth enhancement factor of semiconductor lasers. Linewidth enhancement factor in semiconductor lasers subject to. They do not significantly affect the onset of the qs instability the lower current or. Semiconductor laser linewidth measurements for space. The linewidth enhancement factor had previously been identified with gain induced antiguienng effects 9 and with multnstabnlity and hysteresis in external cavity lasers 10. The simulation results show that the power linewidth product can increase by a factor greater than 2 due to lshb for long dfb lasers. Measurement of linewidth enhancement factor of semiconductor lasers using an injectionlocking technique g. Is there a linewidth theory for semiconductor lasers.
Aside from the advantages in size, cost and complexity, sls cover a broad spectral range and may easily be modulated at rates up to several gigahertz. Influence of injectioncurrent noise on the spectral characteristics. The qd dfbs are complex coupled to a lateral chromium grating alongside the ridge waveguide laser cavity su et al. Compact narrowlinewidth integrated laser based on a low. Roundrobin measurements of the linewidth enhancement. The purpose of this letter is to study possible fundamen tal limitations on the dfb laser linewidth. More precisely, it is the width of the power spectral density of the emitted electric field in terms of frequency, wavenumber or wavelength. Spectral linewidth in microcavity surfaceemitting lasers.
In order to account for the linewidth broadening at higher currents. Donati, measurement of the linewidth enhancement factor of semiconductor lasers based on the optical feedback selfmixing effect, ieee photon. Buus, linewidth broadening factor in semiconductor lasers anoverview, ieee j. Developments of narrow linewidth distributedbraggreflection dbr and distributedfeedback dfb lasers are described. This key parameter typically takes values between 2 and 6 in interband lasers with quantum well or quantum dot active media. Spectral linewidth in microcavity surfaceemitting lasers deep blue. Linewidth broadening factor and gain compression in quantum. This theory has important implications on the limits of linewidth reduction by increasing the length of dfb lasers and on possible future device design for coherent optical system. Measuring the linewidth enhancement factor of semiconductor. Measurement of linewidth enhancement factor of semiconductor. An excitonic correction to the relaxation properties is shown to occur provided the binding energy of the.
Kl optimization from the viewpoint of narrow linewidth operation and stable single mode operation is discussed. Linewidth reduction and frequency stabilization of a. Measurement of linewidth enhancement factor of semiconductor lasers using an injectionlocking technique article in ieee photonics technology letters 5. Measurement of linewidth enhancement factor of different. Importance of the microscopic effects on the linewidth. Dynamic line broadening of semiconductor lasers modulated. Laser linewidth in a typical single transversemode hene laser at a wavelength of 632. Spectral linewidth of semiconductor lasers springerlink. As it also results in an additional linewidth broadening of the laser, it is usually referred to as linewidth. This phaseamplitude coupling is a key feature distinguishing semiconductor lasers from any other type of lasers, and is responsible for a much broader linewidth in semiconductor lasers. They found the linewidth to be inversely proportional to power and to have a value of 114 mhz at 1 mw per facet. All measurements were performed with a te cooler at 15 c. Clamping of the linewidth enhancement factor in narrow.
Measurement of the linewidth enhancement factor of. Narrow spectral linewidth semiconductor lasers springerlink. Linewidth broadening factor in semiconductor lasers an overview abstract. Linewidth enhancement factor an overview sciencedirect. Kl optimization from the viewpoint of narrowlinewidth operation and stable single mode operation is. A novel method for extracting the linewidth broadening factor of. Henry stlh theory of laser linewidth in the instance of semiconductor injection lasers. To achieve a narrow laser linewidth, we utilize the high q microring as external cavity feedback and take advantage of the long effective length of the ring. Selfvalidating technique for the measurement of the. Simple method for measuring the linewidth enhancement. For example, it is a measure of linewidth broadening and chirp in directly modulated lasers, and of the strength of phase.
Kruger, simultaneous measurement of the linewidth enhancement factor. Measuring the linewidth enhancement factor of semiconductor lasers based on weak optical feedback effect abstract semiconductor lasers are very different from other lasers because refraction variation cant be avoided when the gain is changed. This method, based on the principle of external optical injection locking, does not require the knowledge of the absolute value of optical injection level. This result suggests that, if the 1f noise component were eliminated, the semiconductor laser linewidth would approach the alreadylow whitenoise line width. Re cently, however, the dshi technique has also been used to measure linewidth in fiber laser systems 21, 3. Measurements of the semiconductor laser linewidth broadening factor. The linewidth of a laser is predicted by schawlowtownes formula 4. A theory of the spectral width of a singlemode semiconductor laser is presented and used to explain the recent measurements of fleming and mooradian on algaas lasers. The method itself provides an estimation of the measurement error, thus selfvalidating the entire procedure.
This behaviour is reminiscent of exciton dephasing in semiconductor quantum wells due to scattering with an acoustic phonon with energy much smaller than k b t, where t is the sample temperature25. Introduction t he linewidth enhancement factor, or factor, is an im. Linewidth broadening due to longitudinal spatial hole burning. Buus, linewidth broadening factor in semiconductor lasersanoverview, ieee j. Linewidth enhancement factor an overview sciencedirect topics. Measurements which demonstrate the strong dependence of the linewidthbroadening factor. Owing to the low density of threading dislocations and resultant high gain, an a h value of 0. This objective is tangible since the 1f noise in semiconductor lasers usually extends only to a few hundred kilohertz.
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