RU2539117C1 - Semiconductor amplifier of optical emission - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: semiconductor amplifier of optical emission includes a heterostructure at the substrate of n-type conductivity consisting of wide-gap emitters of n-type and p-type conductivity, a ducting layer, an active area that includes a quantum-size active layer, facets limiting the crystal the heterostructure layers crosswise, the first ohmic contact at outer side of the substrate and the second ohmic contact at the side of the emitter with p-type conductivity thus forming the amplification area and injection area, and absorption area placed outside limits of the amplification area. At that the amplification and absorption areas are coupled optically through a part of the ducting layer common for the amplification and absorption areas, the third ohmic contact is formed for the absorption, it is located from the side of the emitter with p-type conductivity, which geometric dimensions are defined according to the preset ratio. Electric insulation of the second and third ohmic contacts is ensured by etched mesa cavity or by etching of a part of the emitter with p-type conductivity.

EFFECT: ensuring simplification of processes, increasing optical power of the input laser pulse.

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Description

The present invention relates to quantum electronics and quantum amplifiers, in particular to semiconductor optical laser amplifiers.

For a wide range of practical applications, laser sources with high pulsed power, a narrow line of the generation spectrum and a single-mode radiation structure are required: wireless optical communication, nonlinear optics (obtaining higher harmonics - transition to the visible region of the spectrum, terahertz radiation generation), time-resolved spectroscopy, metrological tasks (atomic spectroscopy, clock standards), radar systems based on antennas with phased arrays, environmental monitoring systems about space (this includes tasks such as: ranging, measuring the speeds of moving objects and air flows, controlling the chemical composition).

It is known that lasers based on semiconductor heterostructures are capable of demonstrating emissive characteristics with parameters necessary for practical applications: high pulsed power (IS Tarasov, NA Pikhtin, SO Slipchenko, ZN Sokolova, DA Vinokurov, VA Kapitonov, MA Khomylev, A.Yu. Leshko , AV Lyutetskiy, AL Stankevich. High Power Lasers Based on Low Internal Loss Asymmetric Separate Confinement Quantum Well Heterostructures. (Review) Spectrochimica Acta Part A 66 (2007), issues 4-5, (April), 819-823), narrow line generation spectrum (V.V. Vasilieva, D.A. Vinokurov, V.V. Zolotarev, A.Yu. Leshko, A.N. Petrunov, N.A. Pikhtin, M.G. Rastegaeva, Z.N. Sokolova , I.S. Shash in, I.S. Tarasov, High-order diffraction gratings for high-power semiconductor lasers, FTP, 2012, Volume 46, Issue 2) and a single-mode radiation structure (A.Yu. Leshko, A.V. Lyutetskiy, N.A. Pikhtin, S.O. Slipchenko, Z.N. Sokolova, N.V. Fetisova, E.G. Golikova *, Yu.A. Ryaboshtan *, I.S. Tarasov. Powerful single-mode laser diodes based on quantum-size InGaAsP / InP-heterostructures (lambda = 1.3-1.6 μm), FTP, 2002, Volume 36, Issue 11). Moreover, such emitters are characterized by small dimensions, high energy efficiency and low cost. However, the problem is that it is impossible to simultaneously achieve the required values of all parameters within a single monolithic semiconductor laser (P.W. Juodawlkis, JJ Plant, W. Loh, LJ Missaggia, FJ O'Donnell, DC Oakley, A. Napoleone, J Klamkin, JT Gopinath, DJ Ripin, S. Gee, PJ Delfyett, JP Donnelly. High-Power, Low-Noise 1.5-µm Slab-Coupled Optical Waveguide (SCOW) Emitters: Physics, Devices, and Applications. J. of Selected topics in Quantum Electronics. 2011. Vol.17, No.6. p. 1698). Fundamentally, for a semiconductor laser, it is possible to obtain single-mode laser radiation with a narrow generation spectrum line, but a low output optical power. The problem of increasing the output optical power is solved by creating laser systems based on semiconductor optical radiation amplifiers. The general principle of the operation of such a system is that low-power radiation from a master laser generator, characterized by a narrow spectrum and a single-mode structure, is introduced into semiconductor optical radiation amplifiers. As a result, at the output of the amplifier, radiation of higher power is generated with the same spectral and mode parameters.

A semiconductor optical radiation amplifier is known (see US Pat. No. 2002154393), which includes a fundamental mode waveguide that propagates light with a fundamental mode structure, a first multimode waveguide that is wider than a fundamental mode waveguide and is optically coupled to the waveguide for fundamental mode, and provides the propagation of mode structures, the second multimode waveguide, which has a larger width than the first multimode waveguide, and is optically coupled to the first multimode waveguide, and provides distribution of modal structures.

A disadvantage of the known semiconductor optical radiation amplifier is the lack of additional technical solutions providing an increase in internal optical loss in passive regions, as a result of which the working value of the gain is much lower due to the saturation effect beyond the threshold of closed-mode generation.

Known semiconductor optical radiation amplifier (see patent US 2005111079). The device of the known semiconductor optical radiation amplifier includes a signal waveguide for driving the optical signal along the signal path, and further consisting of one or more laser resonators having a gain region lying outside the signal waveguide, the gain region is sufficiently close to the signal waveguide, so that when the region gain is pumped by current, the optical signal passing further along the signal waveguide is amplified due to extremely weak coupling with the laser cavity. When the amplification region is sufficiently pumped to provide laser generation in the laser cavity, saturation of the amplification of the optical signal is achieved. Additional features associated with a segmented laser resonator include separate pumping of the laser resonator region, the grating region, and current profiling, which improves the noise characteristics of the device, suppression of the mutual influence effect during injection, the possibility of manipulating peak amplification, integration with a photodetector, and integration with a modulator.

A disadvantage of the known semiconductor optical radiation amplifier is the lack of additional technical solutions providing an increase in internal optical loss in passive regions, as a result of which the working value of the gain is much lower due to the saturation effect beyond the threshold of closed-mode generation.

A semiconductor optical radiation amplifier is known (see patent US 2007258495), which consists of an active waveguide, an active waveguide including a first waveguide that supports many modes, including the fundamental mode, and a second waveguide, which is wider than the first waveguide, and supports a multimode structure , in which the fundamental mode is provided by the generation of light from an active waveguide.

A disadvantage of the known semiconductor optical radiation amplifier is the lack of additional technical solutions providing an increase in internal optical loss in passive regions, as a result of which the working value of the gain is much lower due to the saturation effect beyond the threshold of closed-mode generation.

Known semiconductor optical radiation amplifier (see patent US 2012243074). Known semiconductor optical radiation amplifier includes an input surface of the waveguide section of the optical amplifier, which has a first covering layer. The output surface of the waveguide section of the optical amplifier, which is connected to the input surface of the waveguide section of the optical amplifier and having a second active covering layer that is wider than the first covering layer. The width of the first active coating layer and the relative difference in the refractive index between the first active coating layer and the adjustment layer of the emitter section in the width direction of the second active coating layer are set so that the carrier density and optical limiting factor in the first active coating layer are higher than the carrier density and factor optical restriction in the second active coating layer.

A semiconductor optical radiation amplifier consists of section 1 — the input side and the input waveguide of the amplifier, section 2 — the output side and the output waveguide of the amplifier associated with the input waveguide of the amplifier, the input light signal of the amplifier, which comes from the input section 1 and exits as the output optical signal from output side of section 2. Electrical contacts to the upper layers are formed only to the injection area, the rest of the surface of the upper layer of section 1 is coated with polyamide, and the surface of section 2 is not coated melted by the contact, covered by a protective dielectric.

A disadvantage of the known semiconductor optical radiation amplifier is the lack of additional technical solutions providing an increase in internal optical loss in passive regions, as a result of which the working value of the gain is much lower due to the saturation effect beyond the threshold of closed-mode generation.

A semiconductor optical radiation amplifier is known (see N. Michel, M. Ruiz, M. Calligaroa, Y. Robert, M. Lecomte, O. Parillauda, M. Krakowski, I. Esquivias, H. Odriozola, JMG Tijerob, CH Kwokc, RV Pentyc, IH White. - Two-sections tapered diode lasers for 1 Gbps free-space optical communications with high modulation efficiency Novel In-Plane Semiconductor Lasers IX. - Proc. Of SPIE Vol.7616, 76161F · 2010 SPIE · CCC code: 0277-786X / 10 / $ 18 · doi: 10.1117 / 12.840702) based on AlGaAs / InGaAs / GaAs heterostructures, an integrated small-signal laser pulse generator 1 mm long, representing a strip design, bounded in the longitudinal direction by etched mesos Grooves, and an optical semiconductor first amplifier 2 mm long, characterized by expanding in the plane of the heterostructure layers at an angle of 40 ° injection area. The integrated low-signal laser pulse generator and the optical semiconductor amplifier were electrically isolated from each other. A peak power of 530 mW was obtained by generating a random train of pulses. The achieved impulse characteristics were obtained by continuously pumping the amplification section with a current of 1.1 A and pulsed pumping of the current control section with an amplitude of 48 mA. The physical principle of the proposed design was as follows: the optical pulse generated by the pulsed pump current in the integrated low-signal laser pulse generator was amplified by propagating in an optical semiconductor amplifier.

A disadvantage of the known semiconductor optical radiation amplifier is the lack of additional technical solutions providing an increase in internal optical loss in passive regions, as a result of which the working value of the gain is much lower due to the saturation effect beyond the threshold of closed-mode generation.

The closest in technical essence and combination of essential features is a semiconductor optical radiation amplifier (see X. Wang, G. Erbert, H. Wenzel, B. Eppich, P. Crump, A. Ginolas, J. Fricke, F. Bugge, M Spreemann and G. Trankle. High-power, spectrally stabilized, near-diffraction-limited 970 nm laser light source based on truncated-tapered semiconductor optical amplifiers with low confinement factors, Semicond. Sci. Technol. 27 (2012) 015010). A semiconductor optical radiation amplifier - a prototype - contains a separate confinement heterostructure, including an expanded waveguide, the confining layers of which are simultaneously emitters of p- and n-type conductivity, an active region consisting of one quantum-dimensional active layer. The semiconductor optical radiation amplifier also contains faces bounding the amplifier crystal in a plane across the layers of the heterostructure. One of the faces is an optical input, and the opposite is an optical output. On the surface of the faces of the optical input and optical output, antireflection coatings are applied. The first ohmic contact is located on the side of the substrate, and the second is on the side of the p-type emitter and forms the amplification region and the injection region. Regions of the crystal outside the amplification region form absorption regions. In the absorption regions, losses are formed due to implantation of ions. The well-known semiconductor optical radiation amplifier ensures the preservation of a single-mode radiation structure in a parallel plane to an output power of about 4 watts.

A disadvantage of the known semiconductor optical radiation amplifier is the complexity of manufacturing technology associated with the need to use the technology of implantation of hydrogen ions in passive regions to suppress the closed mode.

The present invention is to develop such a design of a semiconductor optical radiation amplifier that would simplify the manufacturing technology by removing costly technological processes, while maintaining the functions of an effective optical amplifier, providing an increase in the optical power of the input laser pulse while maintaining its spectral and modal characteristics.

The problem is solved in that the design of the proposed semiconductor optical radiation amplifier includes a heterostructure expressed on an n-type conductivity substrate, consisting of wide-gap emitters of n-type conductivity and p-type conductivity, which are simultaneously layers of optical confinement, a waveguide layer enclosed between them, the active region located therein, including at least one quantum-well active layer, faces bounding the crystal in the direction across the heterostrule layers structures, one of which is an optical input, and the opposite is an optical output, antireflection coatings deposited on the surface of the optical input face and optical output face, the first ohmic contact on the outer side of the substrate and at least one second ohmic contact located on the side of the emitter type of conductivity and forming an amplification region and an injection region, an absorption region located outside the amplification region, wherein the amplification region and the absorption region are optically coupled at least through h part of the waveguide layer common to the amplification and absorption regions, at least one third ohmic contact to the absorption region, located on the side of the p-type emitter, the geometric dimensions of which satisfy the inequality

q · α _max · S _max. ≥k · G _max · S _whisker

k = 1.1

q≥0.5

α _max - the maximum value of optical loss in the absorption region in the absence of the photogenerated charge carriers and Stark effect (cm ^-1), G _max - the material gain in the active area achieved at a given operating current through the second ohmic contact (cm ^-1), S _abs is the area of the third ohmic contact (cm ² ), S _wh is the area of the second ohmic contact (cm ² ), k is the coefficient that takes into account possible inhomogeneities and fluctuations in the amplification region (rel. units), q is the coupling coefficient of the maximum value of optical losses in the region louder in the absence of photogenerated charge carriers and the Stark effect with minimal optical losses in the range of the spectrum of the spontaneous emission of the amplification region under conditions of the complete overlap of the loss spectrum of the absorption region with the spectrum of spontaneous emission of the amplification region (rel. units), and every second ohmic contact is electrically isolated from every third ohmic contact.

Electrical isolation of the second ohmic contact from the third ohmic contact is provided by an etched mesakan or by etching a part of the p-type emitter.

The improvement of such characteristics as simplification of the manufacturing technology of the proposed semiconductor optical radiation amplifier is provided by the inclusion of a third ohmic contact to the absorption region, electrically isolated from the amplification region, providing such optical losses that the threshold conditions for the generation of the closed mode are not satisfied. The use of a gain region with suppressed feedback for spurious mode structures provides an increase in the optical power of the input laser pulse, while maintaining its spectral and modal characteristics.

The inventive injection laser is illustrated by drawings, where

figure 1 shows a known semiconductor optical radiation amplifier;

figure 2 shows the inventive semiconductor optical radiation amplifier;

figure 3 shows the qualitative dependence of the gain in the active region (G _mat ), on the wavelength (λ) at current I1 (curve 1) and current I2> I1 (curve 2), passed through the amplification region; curve 3 — dependence of the photon flux intensity (I _sp ) resulting from spontaneous recombination on the wavelength (λ) for the pump current in the gain region I2; curve 4 — dependence of optical losses in the absorption region (α _decay ) on the wavelength (λ) while maintaining photo-generated charge carriers when the amplification region is pumped by current I2; curve 5 — dependence of optical losses in the absorption region (α _decay ) on the wavelength (λ) during the extraction of photogenerated charge carriers and in the absence of the Stark effect; curve 6 _{shows the} dependence of the optical loss in the absorption region (α _decay ) on the wavelength (λ) during the extraction of photogenerated charge carriers and the presence of the Stark effect.

In the General case, the design of the known semiconductor optical radiation amplifier (figure 1) includes a heterostructure grown on a substrate of n-type conductivity 1, consisting of wide-band emitters of n-type conductivity 2 and p-type conductivity 3, which are both layers of optical limitation, the waveguide layer 4, enclosed between them, the active region 5 located therein, including at least one quantum-well active layer, faces bounding the crystal in a direction transverse to the heterostructure layers 6, 7, 8, 9, o on which is optical input 6, and the opposite 8 is optical output, antireflection coatings 10 deposited on the optical input face and optical output face, the first ohmic contact 11 on the outer side of the substrate and at least one second ohmic contact 12 (dotted with dots), located on the p-type emitter side 3 and forming a gain region 13 (hatched by cross lines) and an injection region 14 (hatched by vertical lines), absorption region 15 (hatched by horizontal ii) located outside the amplification region 13, wherein the amplification regions and the absorption regions are optically coupled through at least a part of the waveguide layer 4 common to the amplification regions 13 and absorption 15. An element 16 providing electrical isolation of the ohmic contact 12 from the absorption region 15 is formed by ion implantation or etched mesakanava.

The design of the proposed semiconductor optical radiation amplifier (Fig. 2) includes a heterostructure expressed on an n-type substrate 1, consisting of wide-gap emitters of n-type conductivity 2 and p-type conductivity 3, which are both layers of optical limitation, waveguide layer 4, concluded between them, the active region 5 located in it, including at least one quantum-dimensional active layer, faces bounding the crystal in the direction across the heterostructure layers 6, 7, 8, 9, one of which x is an optical input 6, and the opposite 8 is an optical output, antireflective coatings 10 deposited on the surface of the optical input face and optical output face, the first ohmic contact 11 on the outer side of the substrate and at least one second ohmic contact 12 (dotted with dots) located from the p-type emitter side 3 and forming the amplification region 13 (shaded by cross lines) and the injection region 14 (shaded by vertical lines), the absorption region 15 (shaded by horizontal lines ii) located outside the amplification region 13, wherein the amplification regions and absorption regions are optically connected through at least a part of the waveguide layer 4 common to the amplification regions 13 and absorption 15, at least one third ohmic contact 17 to the absorption region 15 located from the side of the p-type emitter 3, while every second ohmic contact 12 is electrically isolated from every third ohmic contact 17. An element 16 that provides electrical isolation of the second ohmic contact 12 from the third ohmic a contact 17 is formed or etched mezakanavoy etching part of the emitter p-type conduction 3.

The physical principle of operation of a semiconductor optical radiation amplifier is that a direct current greater than the transparency current, flowing through the amplification region, creates an inverse concentration of electrons in the conduction band and holes in the valence band in the active region, which forms the amplification effect due to flux-induced photons interband optical transitions. The larger the current, the higher the inverse concentration, the greater the gain value can be obtained (figure 3, curve 1, 2). The maximum gain at the transitions between the selected energy states is achieved when the charge carriers completely fill all the energy states of these levels. Electrons in the conduction band and holes in the valence band have a quasi-continuous energy distribution. In this case, the energy range for which the amplification effect is achieved can be quite wide (Fig. 3, curve 1, 2) (S.O. Slipchenko, A.A. Podoskin, N.A. Pikhtin, A.L. Stankevich , NA Rudova, A.Yu. Leshko, IS Tarasov Electroluminescence and absorption spectra of low-loss semiconductor lasers based on InGaAs / AlGaAs / GaAs quantum-well heterostructures, FTP, vol. 45, vol. 5 p.682 (2011)). Because For all radiating devices, the used materials of the active region are direct-gap ones, then in the entire energy interval filled with charge carriers, interband spontaneous radiative recombination occurs, creating a flux of spontaneous photons (Fig. 3, curve 3), including those propagating along the amplification region. In this case, any spurious feedback arising in the crystal of a semiconductor amplifier for spontaneous photons generated by the active medium of the amplification region leads to a decrease in the efficiency of the device and a decrease in the gain. Also, not suppressed feedback leads to the fulfillment of threshold generation conditions for parasitic mode structures, including closed modes that capture absorption regions (S.O. Slipchenko, A.A. Podoskin, N.A. Pikhtin, Z.N. Sokolova, A.Yu. Leshko, IS Tarasov, Analysis of threshold conditions for closed-mode generation in Fabry-Perot semiconductor lasers, FTP, vol. 45, issue 5, p.672 (2011); S.O. Slipchenko, A. A. Podoskin, D.A. Vinokurov, A.L. Stankevich, A.Yu. Leshko, N.A. Pikhtin, V.V. Zabrodsky, I.S. Tarasov.Analysis of the conditions for the disruption of the generation of Fabry-Perot resonator modes half wire dnikovyh lasers with a stripe contact, FTP, t.45, vyp.10, s.1431 (2011)). Because beyond the generation threshold of any mode structure, the gain in the active region is fixed, then, as a result of fulfilling the threshold conditions for the generation of spurious mode structures, a further increase in the gain is impossible. The feedback formed by the faces of the optical input and optical output is suppressed due to antireflection coatings applied to their surface. Feedback for closed mode structures is suppressed by introducing internal modal optical losses into the absorption region greater than the achieved modal gain. A natural source of losses for the absorption region is the interband absorption of the material of the active region. However, for the passive version of the absorption region, when there is only interband absorption of the active region and no additional channels for removing photogenerated charge carriers are used, the flow of spontaneous photons from the amplification region can reduce interband absorption to the state of bleaching (Fig. 3, curve 4). This is due to the fact that, for direct-gap materials, the concentration of accumulated photogenerated carriers in the active region increases with increasing flux of absorbed radiation (S.O. Slipchenko, A.A. Podoskin, D.A. Vinokurov, A.L. Stankevich, A .Yu. Leshko, N.A. Pikhtin, V.V. Zabrodsky, I.S. Tarasov, Analysis of the Failure Conditions for the Mode Production of the Fabry-Perot Resonator in Strip-Contact Semiconductor Lasers, FTP, vol. 45, issue 10, s .1431 (2011); S. Zee, Physics of Semiconductor Devices, Moscow, Mir, 1987). Optical losses in the absorption region can also be formed due to irradiation with ions, which form centers of nonradiative recombination in the semiconductor bulk. However, in this case, it is necessary to use expensive technology, which increases the cost of the amplifier. Proposed in the present invention, a method of increasing internal optical loss is based on the fact that the third ohmic contact formed to the absorption region will effectively increase the amount of optical loss due to two mechanisms. The first mechanism is associated with the suppression of the effect of the accumulation of photogenerated charge carriers in the absorption region due to their extraction upon application of reverse voltage between at least one third ohmic contact of the absorption region and the first ohmic contact (Fig. 3, curve 5). The second mechanism is associated with the use of the quantum-dimensional Stark effect, as a result of which the electric field shifts the absorption spectrum of the active region to the long-wavelength region (Fig. 3, curve 6). In our case, this is the field of the space charge region into which the active region falls. And since the amplification region is characterized by the effect of a shift of the spectrum to the long-wavelength region due to high carrier concentrations (S.O. Slipchenko, A.A. Podoskin, N.A. Pikhtin, A.L. Stankevich, N.A. Rudova, A.Yu. Leshko, IS Tarasov Electroluminescence and absorption spectra of low-loss semiconductor lasers based on InGaAs / AlGaAs / GaAs quantum-well heterostructures, FTP, vol. 45, issue 5, p. 682 (2011)) up to λ _{cr_us} , then the tuning of the spectrum of optical losses of the absorption region with λ _{cr_min} , the wavelength characterizing the absorption edge without taking into account the accumulated photogenerated carriers and the Stark effect, up to λ _{cr_max} , the wavelength characterizing the absorption edge under the Stark effect, provides complete overlap of the spontaneous emission spectra of the gain region and the optical loss spectrum of the absorption region. Taking into account the relation connecting the maximum value of optical losses in the absorption region in the absence of photogenerated charge carriers and the Stark effect (α _max ) (Fig. 3, curve 5) with minimal optical losses during extraction of photogenerated charge carriers and the Stark effect, in the range of the spontaneous spectrum radiation of the amplification region (α _min ) (Fig. 3, curve 6) under conditions of complete overlap of the loss spectrum of the absorption region with the spectrum of spontaneous radiation of the amplification region (Fig. 3, curve 1, 3, 6)

α _min ≥q · α _max , at $$q\ge 0.5(\mathrm{one})$$

q is the coupling coefficient of the maximum value of optical losses in the absorption region in the absence of photogenerated charge carriers and the Stark effect with minimal optical losses in the range of the spectrum of spontaneous emission from the amplification region under conditions of the complete overlap of the loss spectrum of the absorption region with the spectrum of spontaneous emission from the amplification region. To suppress the generation of closed mode structures, the characteristics of the absorption region must satisfy the following inequality

$${\alpha }_{m\mathrm{and}n}\cdot G_{P\mathrm{about}gl}>k\cdot G_{m\mathrm{but}\mathrm{to}\mathrm{from}}\cdot G_{\mathrm{at}\mathrm{from}}(2)$$

where G _max is the maximum value of the material gain in the active region, achieved at a given working current through the second ohmic contact (cm ^-1 ), and _damp is the factor of the optical limitation of the closed mode in the absorption region (relative units). F _yc - optical confinement factor of a closed fashion in the amplification region (RLU), k factor = 1.1 and takes into account possible fluctuations and inhomogeneities in the gain region. Assuming that absorption and amplification occurs in the active region, the optical limitation factors satisfy the expressions

$$G_{P\mathrm{about}gl}=G_{\mathrm{BUT}\mathrm{ABOUT}}\cdot \frac{S_{P\mathrm{about}gl}}{S_{P\mathrm{about}gl}+S_{\mathrm{at}\mathrm{from}}}(3)$$

$$G_{\mathrm{at}\mathrm{from}}=G_{\mathrm{BUT}\mathrm{ABOUT}}\cdot \frac{S_{\mathrm{at}\mathrm{from}}}{S_{P\mathrm{about}gl}+S_{\mathrm{at}\mathrm{from}}}(\mathrm{four})$$

where G _AO is the transverse factor of the optical confinement of the closed mode in the active region, determined by the properties of the waveguide layer and the optical confinement layers (relative units), S _diff is the area of the third ohmic contact (cm ² ), S _yc is the area of the second ohmic contact (cm ² ). Then inequality (2) can be rewritten as

$$q\cdot {\alpha }_{m\mathrm{but}\mathrm{to}\mathrm{from}}\cdot S_{P\mathrm{about}gl}\ge k\cdot G_{m\mathrm{but}\mathrm{to}\mathrm{from}}\cdot S_{\mathrm{at}\mathrm{from}}(5)$$

S _deg = _WL

where W is the width of the third ohmic contact (cm), L is the length of the third ohmic contact (cm). Inequality (5) determines the geometric dimensions of the absorption region, which suppress the generation of closed mode structures when using the method of increasing optical losses based on the extraction of photogenerated carriers and the Stark effect due to the formation of the third ohmic contact.

A real semiconductor optical radiation amplifier operates as follows. Voltages are applied to the first and second ohmic contacts such that the potential difference corresponds to the forward bias of the pn junction in the amplification region. The voltage values are selected based on the required pump current, which provides the required gain. To suppress the generation of closed modes, a voltage is applied to the third ohmic contact such that the potential difference between the third and first ohmic contacts provides a reverse bias of the pn junction in the absorption region. The value of the applied voltage to the third ohmic contact should ensure complete overlap of the spontaneous emission spectra of the gain region and the optical loss of the absorption region, as well as equality (1). Turning on and off the applied voltages to all ohmic contacts must occur simultaneously. After all voltages are turned on, an external signal is input to the amplification region through the optical input. After turning off the external signal for amplification, the voltages can be turned off or remain on until the next external signal for amplification.

Example

To implement a real semiconductor optical radiation amplifier, a heterostructure was fabricated, including an Al _0.1 Ga _0.9 As waveguide layer 2.1 μm thick, sandwiched between a p-type wide-gap Al _0.25 Ga _0.75 As emitter with a thickness of 1.5 μm and a wide-gap Al _0.13 Ga _0.87 As n emitter -conductivity type 2.5 μm thick, the active region consisting of two 8-nm-thick In _0.24 Ga _0.74 As quantum-well active layers separated by a 12 nm GaAs layer located at a distance of 0.6 μm from the wide-gap Al _0.25 Ga _0.75 As p emitter -type carry awns. The width of the optical input was 200 μm and corresponded to the beam width of the external signal. The width of the optical output was also 200 μm; the length of the amplification region was 5 mm. To obtain the required amplification, we apply voltages to the first and second ohmic contacts, which ensure that direct current flows through the amplification region of 10 A. In this case, the maximum gain is 2000 cm ⁻¹ . For the absorption region, the maximum optical loss is α _max = 10000 cm ^-1 . Considering that the long-wavelength boundary of the spectrum of spontaneous emission _{λcr_us} = 1080 nm, and the wavelength of the edge of the optical loss in the absorption region _{λcr_min} = 1060 mn, then to fulfill condition (1), it is necessary to apply a voltage to the third ohmic contact, giving a potential difference of -10 V with the first ohmic contact, then α _min = 7000 cm ^-1 , q = 0.7. In accordance with inequality (5), the absorption section area must satisfy the following expression

$$S_{P\mathrm{about}gl}\ge 3.1\cdot {10}^{-3}{\text{cm}}^{\text{2}}(5)$$

Provided that the length of the first ohmic contact coincides with the length of the amplification region (5 mm), we obtain that the width of the third ohmic contact should be 63 μm. Further, the declared potentials are simultaneously applied to the semiconductor optical radiation amplifier with the selected dimensions of the amplification region and the absorption region, which ensure the forward current flow in the 10 A amplification region and suppress the generation of closed modes. Then, a single-mode optical laser pulse with a duration of 100 ns, an amplitude of 500 mW, and a wavelength of 1065 nm is introduced into the optical input. A single-mode laser pulse with the same spectral characteristics and a power of 6 W is obtained at the optical output. After the input laser pulse is completed, the operating voltage is turned off.

Claims (2)

1. A semiconductor optical radiation amplifier comprising a heterostructure expressed on an n-type conductivity substrate, consisting of wide-gap n-type and p-type emitters, which are both layers of optical confinement, a waveguide layer enclosed between them, the active region located in it comprising at least one quantum-dimensional active layer, faces bounding the crystal in the direction transverse to the heterostructure layers, one of which is an optical input, and false - with an optical output, antireflection coatings deposited on the surface of the optical input face and optical output face, the first ohmic contact on the outer side of the substrate and at least one second ohmic contact located on the p-type emitter side and forming the amplification region and the injection region, an absorption region located outside the gain region, wherein the gain regions and absorption regions are optically coupled through at least a portion of the waveguide layer common to the gain and absorption regions scheniya, characterized in that for the absorption region is formed at least one third ohmic contact disposed on the part of the emitter p-type conduction, the geometrical dimensions of which satisfy the relationships:
q · α _max · S _max. ≥k · G _max · S _whisker
k = 1.1
q≥0.5
α _max - the maximum value of the optical loss in the absorption region in the absence of photogenerated charge carriers and the Stark effect (cm ^-1 ),
G _max - material gain in the active region, achieved at a given working current through the second ohmic contact (cm ^-1 ),
S _pogl - the area of the third ohmic contact (cm ² ),
S _yc is the area of the second ohmic contact (cm ² ),
k - coefficient takes into account possible inhomogeneities and fluctuations in the amplification region (relative units),
q is the coupling coefficient of the maximum value of the optical loss in the absorption region in the absence of photogenerated charge carriers and the Stark effect with minimal optical loss in the range of the spectrum of spontaneous emission of the amplification region under conditions of the complete overlap of the loss spectrum of the absorption region with the spectrum of spontaneous emission of the amplification region (rel. ,
wherein every second ohmic contact is electrically isolated from every third ohmic contact. 2. The semiconductor optical radiation amplifier according to claim 1, characterized in that the electrical isolation of the second ohmic contact from the third ohmic contact is provided by etched mesakanova or by etching part of the p-type emitter.

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