Kruger, simultaneous measurement of the linewidth enhancement factor. In order to account for the linewidth broadening at higher currents. Linewidth broadening factor in semiconductor lasers an overview abstract. Refraction variation can be introduced the theory of semiconductor laser by a dimensional parameter. Linewidth broadening due to longitudinal spatial hole burning. The method itself provides an estimation of the measurement error, thus selfvalidating the entire procedure.
Fm is the fm efficiency mhzma, i b is the bias current level above threshold, and. The linewidth enhancement factor, also known as the. 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. Linewidth broadening factor of a microcavity semiconductor. Clamping of the linewidth enhancement factor in narrow.
On the other hand, the laser linewidth from stabilized lowpower continuouswave lasers can be very narrow and reach down to less than 1 khz. Oct 29, 2019 this work reports the linewidth broadening factor lbf of a continuouswave interband cascade laser operated both below and above threshold. Buus, linewidth broadening factor in semiconductor lasers anoverview, ieee j. Intrinsic homogeneous linewidth and broadening mechanisms of. 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 method is based on the selfmixing effect when a small portion. Air force phillips lab, kirtland afb, nm 87117, usa 3 permanent address. Semiconductor laser linewidth measurements for space.
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. Theory of the linewidth of semiconductor lasers ieee. Measurements which demonstrate the strong dependence of the linewidthbroadening factor. Using the hakkipaoli method, the belowthreshold lbfs around the gain peak are determined to be in the range of 1. This objective is tangible since the 1f noise in semiconductor lasers usually extends only to a few hundred kilohertz. Influence of injectioncurrent noise on the spectral characteristics. 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.
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. A novel method for extracting the linewidth broadening factor of. 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. Linewidth broadening factor of an interband cascade laser. Is there a linewidth theory for semiconductor lasers. This result suggests that, if the 1f noise component were eliminated, the semiconductor laser linewidth would approach the alreadylow whitenoise line width. 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.
Buus, linewidth broadening factor in semiconductor lasersanoverview, ieee j. The emission linewidth above threshold is measured in a gaasalgaas microcavity surface. Oka mura and iwatsuki 3 used a dhsi system with a 72 km fiber delay line to measure the linewidth of an erbium. Rp photonics encyclopedia linewidth, bandwidth, laser. Measurement of linewidth enhancement factor of semiconductor lasers using an injectionlocking technique article in ieee photonics technology letters 5. Laser linewidth in a typical single transversemode hene laser at a wavelength of 632. The consequences for the linewidth and transient wavelength chirping in 1. Roundrobin measurements of linewidth enhancement factor of. The linewidth enhancement factor had previously been identified with gain induced antiguienng effects 9 and with multnstabnlity and hysteresis in external cavity lasers 10. Dynamics and spectral characteristics of quantum dot.
The linewidth of a laser is predicted by schawlowtownes formula 4. Linewidth reduction and frequency stabilization of a. Buus, linewidth broadening factor in semiconductorlasers an overview, ieee j. This key parameter typically takes values between 2 and 6 in interband lasers with quantum well or quantum dot active media. Buus, linewidth broadening factor in semiconductor lasers an overview, ieee j. Although this formula predicts the linewidth satisfactorily for gas lasers, it fails to predict the linewidth for semiconductor lasers.
Narrow spectral linewidth semiconductor lasers springerlink. The semiconductor diode laser sl has a number of properties that make it a desirable. Bhattacharyya, role of linewidth enhancement factor on the frequency response of the synchronized quantum cascade laser, opt. We also need expressions for the light coming out of the laser. The qd dfbs are complex coupled to a lateral chromium grating alongside the ridge waveguide laser cavity su et al. The analysis of different material demonstrates that the. Moloneyl 1 arizona center for mathematical sciences, university of arizona, tucson az 85721, usa 2 us.
The factor 12 serves to convert the change of power gain. Osa linewidth enhancement factor in semiconductor lasers. Owing to the low density of threading dislocations and resultant high gain, an a h value of 0. Clamping of the linewidth enhancement factor in narrow quantumwell grinsch semiconductor lasers j. Cthk1 linewidth enhancement factor of semiconductor. 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. The linewidth of qd dfbs with different gain offsets and a commercial 1. Dynamic line broadening of semiconductor lasers modulated at. There was no ob served decrease in the laser linewidth due to this system. Measurement of the linewidth enhancement factor of. 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. Semiconductor lasers are the most notable of these.
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. The parameter that quantifies the magnitude of this effect is the linewidth broadening factor lbf, also known as. Linewidth enhancement factor an overview sciencedirect topics. This work reports on the ultralow linewidth enhancement factor a hfactor of semiconductor quantum dot lasers epitaxially grown on silicon. Osa selfvalidating technique for the measurement of the.
Laser linewidth theory was pioneered by schawlow and townes 1 and further developed in 2 and 3. Pdf linewidth broadening factor of an interband cascade. Buus, linewidth broadening factor in semiconductor lasersan overview, ieee j. 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. Compact narrowlinewidth integrated laser based on a low. Linewidth enhancement factor an overview sciencedirect. We also discuss the various factors influencing the linewidth in microcavity and strained quantum well lasers. 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.
Semiconductor lasers are very different from other lasers because refraction variation cant be avoided when the gain is changed. 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. We also discuss the various factors influencing the linewidth in microcavity and strained quantum well lasers and the relation between lasing threshold. We discuss the status of the schawlowtowneslaxhenry stlh theory of laser linewidth in the instance of semiconductor injection lasers. They do not significantly affect the onset of the qs instability the lower current or. The purpose of this letter is to study possible fundamen tal limitations on the dfb laser linewidth. 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. A theoretical analysis for gigabitsecond pulse code modulation of semiconductor. The design of a narrowlinewidth dbr laser is described in detail.
Novel measurement technique of alpha factor in dfb. The design of a narrow linewidth dbr laser is described in detail. The gain offset is defined as the difference between the dfb wavelength and the gain. Selfvalidating technique for the measurement of the. Developments of narrow linewidth distributedbraggreflection dbr and distributedfeedback dfb lasers are described. They found the linewidth to be inversely proportional to power and to have a value of 114 mhz at 1 mw per facet. Rp photonics encyclopedia linewidth enhancement factor. At injection levels i below threshold i linewidth enhancement fador in single quantumwell grinsch semiconductor lasers is investigated theoretidy and experimentally. More precisely, it is the width of the power spectral density of the emitted electric field in terms of frequency, wavenumber or wavelength. 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. The simulation results show that the powerlinewidth product can increase by a factor greater than 2 due to lshb for long dfb lasers. A new method for measuring the linewidth enhancement factor. Measurements of the semiconductor laser linewidth broadening factor.
The simulation results show that the power linewidth product can increase by a factor greater than 2 due to lshb for long dfb lasers. Spectral linewidth of semiconductor lasers springerlink. One property that distinguishes semiconductor lasers from most other laser systems is that there is a strong. Spectral linewidth in microcavity surfaceemitting lasers deep blue. Spectral linewidth in microcavity surfaceemitting lasers. Henry stlh theory of laser linewidth in the instance of semiconductor injection lasers. As it also results in an additional linewidth broadening of the laser, it is usually referred to as linewidth. The semiconductor diode laser sl has a number of properties that make it a desirable light source for spectroscopy.
Quantum cascade laser, linewidth enhancement factor, optical. An excitonic correction to the relaxation properties is shown to occur provided the binding energy of the. Indexing terms measurement, semiconductor lasers a simple and accurate method to measure the linewidth enhancement factor u in dfb semiconductor lasers is pro posed. The value of lef is very important for many aspects of laser. Thermally insensitive determination of the linewidth broadening factor in nanostructured semiconductor lasers using optical injection locking. This parameter is called linewidth enhancement factor lef. Measurement of linewidth enhancement factor of different. Measuring the linewidth enhancement factor of semiconductor. Linewidth broadening factor and gain compression in quantum.
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. Cthk1 linewidth enhancement factor of semiconductor lasers. The measured linewidth broadening factor is in good agreement with theoretical calculations that include the most important many. 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. Linewidth enhancement factor 1, also know as chirp parameter or. Thermally insensitive determination of the linewidth. 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.
Linewidth broadening factor in semiconductor lasers ieee xplore. Measurement of linewidth enhancement factor of semiconductor. Only the photons that leave the cavity from the mirrors constitute useful output. Pdf chapter 4 determination of linewidth enhancement. 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. The gain and absorber linewidth enhancement factors. Using the hakkipaoli method, the belowthreshold lbfs. This value is 30 times greater than can be explained by existing theories. Donati, measurement of the linewidth enhancement factor of semiconductor lasers based on the optical feedback selfmixing effect, ieee photon. 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. Semiconductor quantum dot lasers epitaxially grown on.
Linewidth broadening due to longitudinal spatial hole. Measurement of linewidth enhancement factor of semiconductor lasers using an injectionlocking technique g. This work reports the linewidth broadening factor lbf of a continuouswave interband cascade laser operated both below and above threshold. For example, it is a measure of linewidth broadening and chirp in directly modulated lasers, and of the strength of phase. Introduction the most important property of lasers not captured by semiclassical theories, which treat the. An improved delayed selfheterodyne interferometer for. The linewidth broadening factor of semiconductor lasers, which is also known as. 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. Linewidth broadening factor and optical feedback sensitivity. Jun 15, 2016 thermally insensitive determination of the linewidth broadening factor in nanostructured semiconductor lasers using optical injection locking. Intrinsic homogeneous linewidth and broadening mechanisms. Roundrobin measurements of the linewidth enhancement. Linewidth broadening factor and gain compression in.
Kl optimization from the viewpoint of narrowlinewidth operation and stable single mode operation is. Dynamic line broadening of semiconductor lasers modulated. Linewidth enhancement factor in semiconductor lasers subject to. This paper investigates the dynamical and nonlinear properties of silicon based qd lasers through the prism of the linewidth broadening factor i. A novel method for extracting the linewidth broadening. Simple method for measuring the linewidth enhancement. Importance of the microscopic effects on the linewidth. Linewidth broadening factor in semiconductor lasersan. Developments of narrowlinewidth distributedbraggreflection dbr and distributedfeedback dfb lasers are described. Roundrobin measurements of linewidth enhancement factor.
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