Donati, measurement of the linewidth enhancement factor of semiconductor lasers based on the optical feedback selfmixing effect, ieee photon. Although this formula predicts the linewidth satisfactorily for gas lasers, it fails to predict the linewidth for semiconductor lasers. The consequences for the linewidth and transient wavelength chirping in 1. The linewidth enhancement factor, also known as the. We also discuss the various factors influencing the linewidth in microcavity and strained quantum well lasers and the relation between lasing threshold. Linewidth enhancement factor in semiconductor lasers subject to. At injection levels i below threshold i linewidth enhancement fador in single quantumwell grinsch semiconductor lasers is investigated theoretidy and experimentally. Owing to the low density of threading dislocations and resultant high gain, an a h value of 0.
Dynamic line broadening of semiconductor lasers modulated. Semiconductor lasers are the most notable of these. 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. 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. Buus, linewidth broadening factor in semiconductor lasersan overview, ieee j. 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. Fm is the fm efficiency mhzma, i b is the bias current level above threshold, and.
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. Spectral linewidth in microcavity surfaceemitting lasers deep blue. Moloneyl 1 arizona center for mathematical sciences, university of arizona, tucson az 85721, usa 2 us. In order to account for the linewidth broadening at higher currents.
This parameter is called linewidth enhancement factor lef. The analysis of different material demonstrates that the. The linewidth of qd dfbs with different gain offsets and a commercial 1. Intrinsic homogeneous linewidth and broadening mechanisms. This work reports on the ultralow linewidth enhancement factor a hfactor of semiconductor quantum dot lasers epitaxially grown on silicon. Pdf linewidth broadening factor of an interband cascade. We also discuss the various factors influencing the linewidth in microcavity and strained quantum well lasers. Linewidth broadening factor and gain compression in. The emission linewidth above threshold is measured in a gaasalgaas microcavity surface.
The method itself provides an estimation of the measurement error, thus selfvalidating the entire procedure. Measurement of linewidth enhancement factor of semiconductor. Air force phillips lab, kirtland afb, nm 87117, usa 3 permanent address. 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. Intrinsic homogeneous linewidth and broadening mechanisms of. Kl optimization from the viewpoint of narrowlinewidth operation and stable single mode operation is. 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. Kruger, simultaneous measurement of the linewidth enhancement factor. Developments of narrowlinewidth distributedbraggreflection dbr and distributedfeedback dfb lasers are described. An excitonic correction to the relaxation properties is shown to occur provided the binding energy of the. Oka mura and iwatsuki 3 used a dhsi system with a 72 km fiber delay line to measure the linewidth of an erbium.
The simulation results show that the powerlinewidth product can increase by a factor greater than 2 due to lshb for long dfb lasers. Laser linewidth in a typical single transversemode hene laser at a wavelength of 632. This work reports the linewidth broadening factor lbf of a continuouswave interband cascade laser operated both below and above threshold. The factor 12 serves to convert the change of power gain. We also need expressions for the light coming out of the laser. Introduction the most important property of lasers not captured by semiclassical theories, which treat the. Compact narrowlinewidth integrated laser based on a low.
The parameter that quantifies the magnitude of this effect is the linewidth broadening factor lbf, also known as. Measurement of linewidth enhancement factor of semiconductor lasers using an injectionlocking technique g. 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. Narrow spectral linewidth semiconductor lasers springerlink. Refraction variation can be introduced the theory of semiconductor laser by a dimensional parameter. There was no ob served decrease in the laser linewidth due to this system. Laser linewidth theory was pioneered by schawlow and townes 1 and further developed in 2 and 3. Introduction t he linewidth enhancement factor, or factor, is an im. A novel method for extracting the linewidth broadening factor of. Linewidth broadening factor in semiconductor lasersan. 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. An improved delayed selfheterodyne interferometer for. Rp photonics encyclopedia linewidth, bandwidth, laser.
Linewidth broadening factor and optical feedback sensitivity. The purpose of this letter is to study possible fundamen tal limitations on the dfb laser linewidth. 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. Kl optimization from the viewpoint of narrow linewidth operation and stable single mode operation is discussed.
Pdf chapter 4 determination of linewidth enhancement. 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. Only the photons that leave the cavity from the mirrors constitute useful output. The linewidth of a laser is predicted by schawlowtownes formula 4. Using the hakkipaoli method, the belowthreshold lbfs around the gain peak are determined to be in the range of 1. Linewidth broadening due to longitudinal spatial hole. They do not significantly affect the onset of the qs instability the lower current or.
Osa linewidth enhancement factor 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. The measured linewidth broadening factor is in good agreement with theoretical calculations that include the most important many. Buus, linewidth broadening factor in semiconductor lasersanoverview, ieee j. Semiconductor laser linewidth measurements for space. The design of a narrowlinewidth dbr laser is described in detail. Semiconductor lasers are very different from other lasers because refraction variation cant be avoided when the gain is changed.
The semiconductor diode laser sl has a number of properties that make it a desirable. The value of lef is very important for many aspects of 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. Jun 15, 2016 thermally insensitive determination of the linewidth broadening factor in nanostructured semiconductor lasers using optical injection locking.
A firstorder frequencydependent formula of the linewidth broadening factor. This result suggests that, if the 1f noise component were eliminated, the semiconductor laser linewidth would approach the alreadylow whitenoise line width. This value is 30 times greater than can be explained by existing theories. 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 key parameter typically takes values between 2 and 6 in interband lasers with quantum well or quantum dot active media. The design of a narrow linewidth dbr laser is described in detail. Developments of narrow linewidth distributedbraggreflection dbr and distributedfeedback dfb lasers are described. Measurements which demonstrate the strong dependence of the linewidthbroadening factor. This paper investigates the dynamical and nonlinear properties of silicon based qd lasers through the prism of the linewidth broadening factor i. 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. Buus, linewidth broadening factor in semiconductor lasers anoverview, 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.
Thermally insensitive determination of the linewidth. In semiconductor lasers, spontaneous emission events affect carrie r density, resulting in refractive index and phase changes, thus broadening the linewidth 29. Roundrobin measurements of the linewidth enhancement. Roundrobin measurements of linewidth enhancement factor.
This method, based on the principle of external optical injection locking, does not require the knowledge of the absolute value of optical injection level. As it also results in an additional linewidth broadening of the laser, it is usually referred to as linewidth. Novel measurement technique of alpha factor in dfb. Dynamic line broadening of semiconductor lasers modulated at. 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.
This objective is tangible since the 1f noise in semiconductor lasers usually extends only to a few hundred kilohertz. Spectral linewidth in microcavity surfaceemitting lasers. Measurement of linewidth enhancement factor of different. Measuring the linewidth enhancement factor of semiconductor. Linewidth broadening factor in semiconductor lasers ieee xplore. More precisely, it is the width of the power spectral density of the emitted electric field in terms of frequency, wavenumber or wavelength. The linewidth enhancement factor had previously been identified with gain induced antiguienng effects 9 and with multnstabnlity and hysteresis in external cavity lasers 10. 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.
Is there a linewidth theory for semiconductor lasers. The simulation results show that the power linewidth product can increase by a factor greater than 2 due to lshb for long dfb lasers. Rp photonics encyclopedia linewidth enhancement factor. Roundrobin measurements of linewidth enhancement factor of. Spectral linewidth of semiconductor lasers springerlink. Linewidth broadening factor and gain compression in quantum.
Clamping of the linewidth enhancement factor in narrow. Using the hakkipaoli method, the belowthreshold lbfs. Thermally insensitive determination of the linewidth broadening factor in nanostructured semiconductor lasers using optical injection locking. Linewidth broadening factor of an interband cascade laser. We discuss the status of the schawlowtowneslaxhenry stlh theory of laser linewidth in the instance of semiconductor injection lasers. Linewidth enhancement factor an overview sciencedirect. Selfvalidating technique for the measurement of the. The qd dfbs are complex coupled to a lateral chromium grating alongside the ridge waveguide laser cavity su et al. 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 linewidth broadening factor of semiconductor lasers, which is also known as. Measurements of the semiconductor laser linewidth broadening factor. Clamping of the linewidth enhancement factor in narrow quantumwell grinsch semiconductor lasers j.
Linewidth broadening factor in semiconductor lasers an overview abstract. Quantum cascade laser, linewidth enhancement factor, optical. The semiconductor diode laser sl has a number of properties that make it a desirable light source for spectroscopy. Linewidth broadening factor of a microcavity semiconductor. Influence of injectioncurrent noise on the spectral characteristics. Henry stlh theory of laser linewidth in the instance of semiconductor injection lasers. This method is based on the selfmixing effect when a small portion. Buus, linewidth broadening factor in semiconductor lasers an overview, ieee j. Measurement of the linewidth enhancement factor of. A novel method for extracting the linewidth broadening. 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. One property that distinguishes semiconductor lasers from most other laser systems is that there is a strong.
Linewidth broadening due to longitudinal spatial hole burning. 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 enhancement factor 1, also know as chirp parameter or. The gain offset is defined as the difference between the dfb wavelength and the gain. Linewidth reduction and frequency stabilization of a. The gain and absorber linewidth enhancement factors. Semiconductor quantum dot lasers epitaxially grown on. Cthk1 linewidth enhancement factor of semiconductor. Linewidth enhancement factor an overview sciencedirect topics.
Osa selfvalidating technique for the measurement of the. A theoretical analysis for gigabitsecond pulse code modulation of semiconductor. 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. A new method for measuring the linewidth enhancement factor. Theory of the linewidth of semiconductor lasers ieee. 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. Simple method for measuring the linewidth enhancement. Buus, linewidth broadening factor in semiconductorlasers an overview, ieee j. On the other hand, the laser linewidth from stabilized lowpower continuouswave lasers can be very narrow and reach down to less than 1 khz. Cthk1 linewidth enhancement factor of semiconductor lasers. Dynamics and spectral characteristics of quantum dot. Re cently, however, the dshi technique has also been used to measure linewidth in fiber laser systems 21, 3.