Showing papers on "Semiconductor optical gain published in 1982"
TL;DR: In this article, a theory of the spectral width of a single-mode semiconductor laser is presented and used to explain the recent measurements of Fleming and Mooradian on AlGaAs lasers.
Abstract: A theory of the spectral width of a single-mode semiconductor laser is presented and used to explain the recent measurements of Fleming and Mooradian on AlGaAs lasers. They found the linewidth to be inversely proportional to power and to have a value of 114 MHz at 1 mW per facet. This value is 30 times greater than can be explained by existing theories. The enhanced linewidth is attributed to the variation of the real refractive index n' with carrier density. Spontaneous emission induces phase and intensity changes in the laser field. The restoration of the laser to its steady-state intensity results in changes in the imaginary part of the refractive index \Delta n" . These changes are accompanied by changes in the real part of the refractive index \Delta n' , which cause additional phase fluctuations and line broadening. The linewidth enhancement is shown to be 1 + \alpha^{2} , where \alpha = \Delta n'/\Delta n" . A value of \alpha \approx 5.4 , needed to explain the observed linewidth, is close to the experimental values of a of 4.6 and 6.2.
2,293 citations
NEC1
TL;DR: In this article, the injected carrier density dependent refractive index in the active region of a semiconductor laser has been analyzed, and it has been found that this dependence significantly affects the injection locking properties, giving rise to a peculiar asymmetric tuning curve and dynamic instability.
Abstract: Injection locking properties of a semiconductor laser have been analyzed, taking into account the injected carrier density dependent refractive index in the active region. It has been found that this dependence significantly affects the injection locking properties, giving rise to a peculiar asymmetric tuning curve and dynamic instability. The instability originates from the intermode interaction via the modulation in the injected carrier density caused by intensity beat. The detuning dependence of the direct modulation response characteristics inside and outside of the locking range have also been examined.
646 citations
TL;DR: Optical feedback-induced changes in the output spectra of several GaAlAs laser operating at 0.83 μm are described in this paper. But this work is restricted to a three-mirror cavity, where the feedback radiation from a mirror 60 cm away from the laser is controlled in intensity and phase.
Abstract: Optical feedback-induced changes in the output spectra of several GaAlAs lasers operating at 0.83 μm are described. The feedback radiation obtained from a mirror 60 cm away from the laser is controlled in intensity and phase. Spectral line narrowing or broadening is observed in each laser depending on the feedback conditions. Minimum linewidths observed with feedback are less than 100 kHz. Improved wavelength stability is also obtained with optical feedback resulting in 15 dB less phase noise. An analytical model for the three-mirror cavity is developed to explain these observations.
226 citations
TL;DR: In this paper, simple analytical expressions for the oscillation frequency, quantum FM noise spectrum, oscillation power spectrum, spectral linewidth, and direct optical frequency modulation efficiency in semiconductor lasers with external grating feedback are presented.
Abstract: Simple analytical expressions for the oscillation frequency, quantum FM noise spectrum, oscillation power spectrum, spectral linewidth, and direct optical frequency modulation efficiency in semiconductor lasers with external grating feedback are presented. Experimental results for the grating loaded AlGaAs lasers are in good agreement with the theoretical predictions. Remarkable reduction in spectral linewidth to less than 50 kHz is achieved by feeding back only 10-3of the output power. Oscillation frequency stabilization, frequency jump behavior, and reduction in direct optical frequency modulation efficiency are also discussed.
114 citations
TL;DR: Optical feedback-induced changes in the output spectra of several GaAlAs laser operating at 0.83 µm are described in this article. But this work assumes that the feedback radiation from a mirror 60 cm away from the laser is controlled in intensity and phase.
Abstract: Optical feedback-induced changes in the output spectra of several GaAlAs lasers operating at 0.83 µm are described. The feedback radiation obtained from a mirror 60 cm away from the laser is controlled in intensity and phase. Spectral line narrowing or broadening is observed in each laser depending on the feedback conditions. Minimum linewidths observed with feedback are less than 100 kHz. Improved wavelength stability is also obtained with optical feedback resulting in 15 dB less phase noise. Analytical model for the three-mirror cavity is developed to explain these observations.
102 citations
TL;DR: In this paper, the distortion and noise characteristics of semiconductor lasers in connection with optical fibers are reviewed and the influence of polarization coupling in single-mode fibers on the resulting transmission behavior is discussed.
Abstract: The distortion and noise characteristics of semiconductor lasers in connection with optical fibers are reviewed. In particular, the intrinsic distortions and noise of semiconductor lasers together with the partition noise are discussed followed by a discussion on the influence of reflections. Modal noise phenomena due to the interference pattern at the endface of optical fibers are treated with respect to noise and distortions. Finally, the influence of polarization coupling in single-mode fibers on the resulting transmission behavior is discussed.
78 citations
57 citations
TL;DR: In this article, an incident optical beam, generated by an ordinary semiconductor laser, was injected into the bistable laser with inhomogeneous excitation, and the mutual relation between PI•PO characteristics and I•L characteristics for the Bistable Laser was investigated.
Abstract: Experimental results are presented regarding the switching of a bistable semiconductor laser’s output (PO) with injected optical power (PI). An incident optical beam, generated by an ordinary semiconductor laser, was injected into the bistable semiconductor laser with inhomogeneous excitation. The mutual relation between PI‐PO characteristics and I‐L characteristics for the bistable laser, and the dependence of PI‐PO characteristics on the bias current of the bistable laser are described. Switching between the two stable bistable operation states is accomplished by injecting optical trigger pulses. Switching of the laser having differential gain characteristics, through use of optical pulse, is also looked at.
52 citations
TL;DR: In this paper, the absorption spectrum of water vapor in the (2, 1, 1) vibration-rotation band has been observed by using an AlGaAs semiconductor laser around 0.82 µm.
Abstract: The absorption spectrum of water vapor in the (2, 1, 1) vibration-rotation band has been observed by using an AlGaAs semiconductor laser around 0.82 µm. The laser frequency was stabilized to one of the absorption lines by controlling the injection current. A frequency stability of 1.9×10-9≧σ≧1.1×10-11 was obtained for 10 ms≦τ≦500 s.
50 citations
TL;DR: In this article, a double-heterostructure AlGaAs semiconductor laser was used in an injection-locked mode or in a resonant amplification mode by keeping the drive current above or just below its threshold.
Abstract: Optical FM signal amplification by semiconductor lasers is studied by emphasizing their bandwidth characteristics. The laser is operated either in an injection-locked mode or in a resonant amplification mode by keeping the drive current above or just below its threshold. The bandwidths of both amplifiers are evaluated by the reduction in modulation sidebands and are compared with the bandwidths measured statically by scanning the frequency of incident CW wave. The \sqrt{G}B = 25 GHz gain bandwidth product is obtained for both operation modes using a double heterostructure AlGaAs semiconductor laser. The bandwidth obtained in the above procedure is in good agreement with theoretical results.
49 citations
TL;DR: In this paper, the authors present an analysis of semiconductor lasers of the interferometric and ring types, using the scattering-matrix formulation, to find new applications for semiconductor laser beyond serving merely as a source for coherent radiation.
Abstract: In this paper we present an analysis of semiconductor lasers of the interferometric and ring types, using the scattering-matrix formulation. The purpose of our analysis is to find new applications for semiconductor lasers beyond serving merely as a source for coherent radiation. Potential applications include wavelength stability, possibility for wavelength tuning and switching, operation as a traveling wave laser, and possible reduction in feedback effect. An initial set of experiments has been carried out and the results have borne out some theoretical predictions. These lasers should offer promises for use in integrated optics and fiber optical communication. Furthermore, the scattering-matrix formulation should be useful in treating other complex laser structures and lasers in an optical network environment.
TL;DR: In this article, the spectral properties of two-section GaInAsP/InP laser systems were studied and single-longitudinal mode light pulses of less than 750 ps length were produced by driving the long section of the laser only or by prebiasing the long cavity and modulating the short section with a current pulse of 1 ns halfwidth.
Abstract: The spectral behaviour of monolithic two-section GaInAsP/InP lasers is studied. Single-longitudinal-mode light pulses of less than 750 ps length are produced by driving the long section of the laser only or by prebiasing the long cavity and modulating the short section with a current pulse of 1 ns halfwidth. The wavelength of the output light can be changed by varying the operation temperature or the prebias level.
PARC1
TL;DR: In this article, an analysis of gain-guided diode laser at threshold is presented and the effects of charge induced real refractive index antiguiding and gain-charge density relations are studied in detail.
Abstract: An analysis of gain-guided diode lasers at threshold is presented. After describing the formulation, the effects of charge induced real refractive index antiguiding and gain-charge density relations are studied in detail. Their influence on the threshold current, modal distributions, and the lateral fax-field radiation patterns is discussed. Next a "model" laser is defined and each parameter including dimensions, compositions, stripewidth, diffusion constants, current spreading resistance, and facet reflectivities is individually varied to determine the resulting modifications in laser properties.
CNET1
TL;DR: In this paper, the gain sensitivity of a travelling-wave-type (TW) AlGaAs semiconductor laser amplifier to the input signal polarisation state was investigated and the results showed that the amplifier is gain sensitive.
Abstract: We report experimental results on the gain sensitivity of a travelling-wave-type (TW) AlGaAs semiconductor laser amplifier to the input signal polarisation state.
Patent•
NEC1
TL;DR: In this paper, a multilayer double heterostructure has a stripe geometry with channels formed along both sides of the stripe and extending down to the first cladding layer, in order to block a current flow therethrough.
Abstract: A buried heterostructure semiconductor laser diode with improved efficiency, CW operating temperature and output characteristic is comprised of a semiconductor substrate of a first conductivity type and includes successively at least a first cladding semiconductor layer of the first conductivity type, an active semiconductor layer, and a second cladding semiconductor layer of a second conductivity type. The active semiconductor layer has a narrower bandgap than those of the first and second cladding semiconductor layers. The multilayer double heterostructure has a stripe geometry with channels formed along both sides of the stripe and extending down to the first cladding layer. A current blocking layer is formed on the multilayer double heterostructure except for the top surface of the stripe geometry, in order to block a current flow therethrough.
TL;DR: In this paper, a simple technique whereby phase noise in semiconductor lasers may be reduced was presented. But this technique is not suitable for coherent optical-fibre communications systems and it cannot be applied to optical sensors.
Abstract: There are several applications of highly coherent semiconductor lasers, especially in coherent optical-fibre communications systems and optical-fibre sensors. Optical phase noise is extremely important in these applications. Here we report preliminary results from a simple technique whereby phase noise in semiconductor lasers may be reduced. Initial results demonstrate a phase-noise reduction of typically 20 dB. Developments of the technique should permit reduction towards the shot noise limit.
Patent•
10 Jun 1982TL;DR: In this article, two or more partially reflecting mirrors are coupled to a totally reflecting mirror through the laser gain medium by a grating element, which permits a lower gain line to build up first, followed by a higher gain line, which then terminates the lower line through gain saturation.
Abstract: Multiple wavelengths are produced from a single laser gain medium by utilizing gain saturation effects within the laser cavity. Two or more partially reflecting mirrors are coupled to a totally reflecting mirror through the laser gain medium by a grating element. The optical path lengths defined by each of the partially reflecting mirrors are varied by the positioning of the partially reflecting mirrors. This permits a lower gain line to build up first, followed by a higher gain line, which then terminates the lower gain line through gain saturation. The frequency switching times and pulse intensities of the wavelengths can be varied by varying the optical path lengths.
TL;DR: In this paper, the frequency response of a semiconductor laser amplifier operating just below lasing threshold is investigated experimentally and theoretically and the observed asymmetry is explained in terms of the refractive index change due to decrease in the active region carrier density accompanied by optical amplification.
Abstract: Asymmetry in the frequency response of semiconductor laser amplifiers operating just below lasing threshold is investigated experimentally and theoretically. Frequency response of the amplifier is measured using a transient shift of the oscillation wavelength when the laser is operated in pulsed mode. The observed asymmetry is explained in terms of the refractive index change due to decrease in the active-region carrier density accompanied by optical amplification.
Patent•
24 May 1982TL;DR: In this paper, an optical system for focusing a light beam emitted from a semiconductor laser is described, which comprises a lens of a numerical aperture NA satisfying a relation with respect to the wave front aberration.
Abstract: An optical system for focusing a light beam emitted from a semiconductor laser is disclosed which comprises a lens of a numerical aperture NA satisfying a relation ##EQU1## (where λ and ΔZ indicate a laser wavelength of and an astigmatic focal distance in the semiconductor laser, respectively) to make the wave front aberration of a light beam emerging from the lens smaller than or equal to λ/4, thereby correcting astigmatism in the semiconductor laser.
TL;DR: In this paper, the small-signal modulation response of semiconductor laser with a very small mirror reflectivity was analyzed and the results can serve as useful guides in designing high frequency semiconductor lasers.
Abstract: The small-signal modulation response of semiconductor lasers with a very small mirror reflectivity is analyzed. Superluminescent effects inside the laser cavity provide yet another mechanism for damping relaxation oscillation resonance. These results can serve as useful guides in designing high frequency semiconductor lasers.
TL;DR: In this article, the distortion noise characteristics of semiconductor lasers in connection with optical fibers are reviewed, and the influence of polarization coupling in single-mode fibers on the resulting transmission behavior is discussed.
Abstract: The distortion noise characteristics of semiconductor lasers in connection with optical fibers are reviewed. In particular, the intrinsic distortions, noise of semiconductor lasers together with the partition noise are discussed followed by a discussion on the influence of reflections. Modal noise phenomena due to the interference pattern at the endface of optical fibers are treated with respect to noise, distortions. Finally, the influence of polarization coupling in single-mode fibers on the resulting transmission behavior is discussed.
TL;DR: The external optical feedback system with a diffraction grating and mirrors is designed as a light source system in wavelength division multiplexing transmission as mentioned in this paper, which can select not only oscillation center wavelength but also spectral range in semiconductor lasers by using an identical grating twice.
Abstract: The external optical feedback system with a diffraction grating and mirrors is designed as a light source system in wavelength division multiplexing transmission This system can select not only oscillation center wavelength but also spectral range in semiconductor lasers by using an identical grating twice Experimental results demonstrate selected oscillations of single and double longitudinal modes in a multimode semiconductor laser
TL;DR: In this paper, the electronic band structure of a finite one-dimensional semiconductor is examined and the surface states are identified and the absorption cross-section for transitions to these states is calculated.
TL;DR: In this article, a technique for obtaining multicolor operation of mode-locked laser has been applied to an external-cavity semiconductor laser and the generation of two perfectly synchronized optical pulse trains of different wavelengths from such a laser is demonstrated.
Abstract: A technique for obtaining multicolor operation of mode-locked lasers has been applied to an external-cavity semiconductor laser. The generation of two perfectly synchronized optical pulse trains of different wavelengths from such a laser is demonstrated.
TL;DR: In this paper, a rectangular conical diffractor (RCD) is designed for wavelength division multiple access (WDMA) transmission systems, which is composed of a diffraction grating and a mirror.
Abstract: A new external feedback system named the rectangular conical diffractor (RCD), which is composed of a diffraction grating and a mirror, is designed This system has advantages for wavelength-division-multiplexing transmission systems By using this system in both single and multimode semiconductor lasers: 1) the oscillation wavelength of a semiconductor laser can be selected freely; 2) some semiconductor lasers oscillate at different wavelengths from one another simultaneously, and no interference exists between the oscillation wavelengths under the condition that each semiconductor laser is operated independently; and 3) the selected wavelength is stable against temperature variation of the lasers
TL;DR: In this paper, the influence of spontaneous emission on the axial mode spectrum of semiconductor laser diodes is described by solving the wave equation of each mode and calculating the rate of spontaneous emissions coupled into the mode.
Abstract: The influence of spontaneous emission on the axial mode spectrum of semiconductor laser diodes is described by solving the wave equation of each mode and calculating the rate of spontaneous emission coupled into the mode. Since we employ a quantum mechanical gain model, spectral gain and spontaneous emission are unambiguously correlated to carrier density. Spectra of axial modes are calculated for different power levels, gain widths and cavity lengths.
TL;DR: RCA has recently completed two systems that establish the feasibility of optical disks as a high data-rate digital recording medium and the results are being used to design operational data storage hardware.
Abstract: Today's laser-ablated metal-film optical disksl could be the digital data storage system of the future. They are made of materials that can be stored for many years without stringent environmental controls, and because diffraction-limited optical systems in combination with disks have high storage densities, they promise a lower cost per bit than any other medium. RCA has recently completed two systems that establish the feasibility of optical disks as a high data-rate digital recording medium. The results of these programs are being used to design operational data storage hardware. The systems can record 5 x 1010 bits of data on one side of an optical disk at rates exceeding IOOM bits per second. They have provided a bit error rate of one in 108 and can access any block of data in less than 0.5 seconds. To achieve these results multiple laser spots were focused into a 0.4-Am diameter at half power and spaced on 1.25-nm centers. The disk's aerial density of 109 bits per square inch is an order ofmagniture greater than the generally accepted limit in magnetic recording of 108 bits per square inch.