RU193300U1 - SEMICONDUCTOR SOURCE OF INFRARED RADIATION - Google Patents

Abstract

The invention relates to techniques for semiconductor lasers. The semiconductor infrared radiation source includes a semiconductor substrate (1) with a first resonator (2) on whispering gallery modes (WGM) and a second resonator (3) on WGM in the form of heterostructures. Resonators (2), (3) are optically coupled, and their at least active regions are connected by a jumper (17) of length L and width h, satisfying certain relations. The first ohmic contact (15) is applied to the surface of the semiconductor substrate (1), the opposite surface with the first and second resonators (2, 3), and the second and third ohmic contacts (11, 14) are applied to the end face of the first and second resonators (2, 3). The second resonator (3) from the side opposite the first resonator (2) is truncated along a plane parallel to its axis. The second ohmic contact (11) is made in the form of a half ring, the third ohmic contact (14) is made in the form of a part of the ring, and the fourth ohmic contact (12) in the form of a half ring opposite to the second ohmic contact (11) is applied to the end of the first resonator on the WGM. The technical result consists in providing the possibility of directional removal of radiation, increasing the radiation power and increasing the width of the line of reconstruction of radiation. 3 s.p. f-ly, 5 ill.

Description

The utility model relates to optoelectronic technology, more precisely, to compact sources of laser radiation in the infrared wavelength range, namely to semiconductor single-frequency sources of infrared (IR) radiation based on a laser with a whispering gallery resonator (Whispering Gallery Modes - WGM). These sources of infrared radiation are used in various fields of science and technology, in industry, namely in spectroscopy, in medicine, optical communication and information transfer systems, and in optical superfast computing and switching systems.

Currently, there is an urgent need for single-frequency radiation sources operating in the spectral range of 1.6–5 μm for high-resolution diode laser spectrometers. In this spectral range, there are characteristic absorption lines of a significant number of toxic and harmful gases and liquids, explosives, etc. However, the advantages of optical detection of such substances are not fully utilized due to the lack of simple sources of coherent radiation over this wavelength range.

The active region of a semiconductor laser operating in the mid-IR region of the spectrum is usually a narrow-gap semiconductor. In such semiconductors, nonradiative recombination processes are strong (compared with wide-gap ones), which reduces the gain in the active region. Consequently, the requirements for the quality factor of a laser resonator, which encloses an active region and provides feedback for stimulated emission of light, are increasing. The resonator largely determines not only the size and shape of the laser, but also the radiation parameters: power, directivity and spectral characteristics of the laser.

In lasers with WGM resonators, feedback is performed with the closure of the light beam. Such resonators use the effect of total internal reflection. In a laser with a WGM resonator, light circulates in a circle inside the resonator along its perimeter, repeatedly reflecting from the walls at an angle of inclination greater than the critical angle for total internal reflection. The region of localization of light in such a cavity is several wavelengths from the edge of the cavity. Light losses due to absorption and scattering on surface roughness are minimal due to the high quality factor of the WGM resonator. The main mechanism of optical losses causing a threshold current is the scattering of light by the inhomogeneities of the edges of the resonator. In the IR range, due to the relatively large wavelength, the quality of the semiconductor-air interface is not as significant as for the visible range. Advantages of lasers with a WGM resonator are their manufacturability, low threshold current values, and high Q-factor of the resonator, which allows using materials for the active region with low optical amplification.

A semiconductor infrared radiation source is known (see application US 2009154505, IPC H01S 3/10, published June 18, 2009), including a semiconductor substrate with two geometrically spaced resonators based on A ³ B ⁵ compounds with different radii, optically coupled passive waveguides, a continuous ohmic the contact applied to the surface of the semiconductor substrate, the opposite surface with the resonators, and two ring ohmic contacts, each of which is applied to the end of the corresponding resonator. The coupling of the first and second resonators forms a new doubly coupled resonator, in which stable laser oscillation occurs only at the resonant wavelength at which the two resonators interact at the resonant frequency.

A disadvantage of the known source of infrared radiation is the design complexity, since, in addition to the resonators, it has two more waveguides (input and output), which causes additional optical losses during the transmission of light through the waveguide and complicates the manufacturing technology of the source.

A semiconductor source of infrared radiation is known (see patent EP 1737090, IPC G02B 6/12; G02F 1/01; H01S 5/10, H01S 5/06, published July 18, 2012), including a semiconductor emitter for optical pumping of a laser that transmits light through a fiber optic line to a first resonator containing heating elements used to change the wavelength. The first resonator is optically coupled to the second resonator, which also contains heating elements.

A disadvantage of the known semiconductor source is its complex design due to the presence of fiber optic lines, heating elements and passive resonators, which introduce additional optical losses when transmitting light along the fiber optic line from the source to the resonator. In a known semiconductor source, wavelength control is carried out by heating the resonators.

A semiconductor source of infrared radiation is known (see application US 2017264079, IPC H01S 3/067, H01S 3/08, H01S 5/065, published September 14, 2017) containing a semiconductor substrate on which a laser diode and a unidirectional optically connected to it are located resonator on WGM. The laser diode can be made in the form of a Fabry-Perot (FP) laser diode, a laser diode with distributed feedback (ROS) and a laser diode with a distributed Bragg reflector (RBO).

A disadvantage of the known semiconductor source is the complexity of its design, since it is necessary to use complex and expensive ROS and RBO lasers, as well as an integrated WGM resonator, to ensure single-mode generation. Moreover, in this design there is no possibility of tuning the laser generation line.

A wavelength tunable laser is known (see US Pat. No. 7,664,156, IPC H01S 3/081; H01S 3/083, 02/16/2010), including a substrate with optically coupled and geometrically spaced ring resonators into which light is introduced via fiber optic lines onto ring resonators . To control the wavelength of the ring resonators, heating elements are used.

The known wavelength tunable laser contains numerous additional elements introducing additional optical losses during the transmission of light via fiber optic lines from the light source to the ring resonators.

A known semiconductor source of infrared radiation (see patent RU 2465699, IPC H01S 5/065, H01S 5/10, H01L 27/08, publ. 10/27/2012), which coincides with this technical solution for the largest number of essential features and adopted for the prototype. The semiconductor source prototype includes a semiconductor substrate with two optically coupled and mutually overlapping in the region of the waveguides to the depth D resonators on the WGM in the form of heterostructures containing the active region, the first ohmic contact deposited on the surface of the semiconductor substrate, the opposite surface with resonators on the WGM, and the second and the third ring ohmic contacts. The second and third ohmic contacts are applied to the end of the corresponding resonator. The distance from the outer edge of the second and third ohmic contacts to the outer edge of the resonator does not exceed 100 μm. The depth D of the overlap of the resonators on the WGM satisfies the relation: 0 <D <10λ _to μm, where λ _to is the radiation wavelength (in the crystal) of the semiconductor source of infrared radiation, μm; λ _k = λ / n, where n is the refractive index of a semiconductor crystal.

In a prototype semiconductor source, radiation comes out from all the side surfaces of the resonators due to scattering on the inhomogeneities of the crystal lattice, it does not allow for wide tuning of the source generation line, and the total radiation power varies from 0.5 to 2.0 mW, which significantly narrows the range of applications semiconductor source.

The objective of this technical solution is to develop a semiconductor source of infrared radiation, which would provide directed radiation removal, increased output radiation power and a wider restructuring of the radiation generation line.

The problem is solved in that the semiconductor source of infrared radiation includes a semiconductor substrate with the first and second optically coupled resonators on the WGM in the form of heterostructures containing an active region, the first ohmic contact deposited on the surface of the semiconductor substrate, the opposite surface with the first and second resonators on the WGM, and second and third ohmic contacts applied to the end face of the first and second resonators on the WGM, respectively. The distance from the outer edge of the second and third contacts to the outer edge of the first and second resonators on the WGM, respectively, does not exceed 100 μm. At least the active regions of the first and second resonators on the WGM are connected by a jumper of length L and width h, satisfying the relations:

0 <L <5λ;

0 <h <0.2⋅R;

where λ is the radiation wavelength (in air) of the semiconductor source of infrared radiation, microns;

R is the radius of the resonator, microns.

The second resonator on the WGM from the side opposite the first resonator on the WGM is truncated in a plane parallel to its axis, the second ohmic contact is made in the form of a half ring, the third ohmic contact is made in the form of a part of the ring, and the fourth ohmic contact is applied to the end of the first resonator on the WGM in the form of a half ring opposite to the second ohmic contact.

The second resonator on the WGM can be truncated along the diameter of the resonator.

The first and second resonators on the WGM can be made respectively in the form of a disk and a truncated disk.

The first and second resonators on the WGM can be made respectively in the form of a ring and a truncated ring.

The choice of the boundary values of L and h is due to the following. At L≥5λ, radiation flows from one resonator to another worse, which complicates the appearance of a single-mode lasing regime. For h≥0.2⋅R, the cavity is already too deformed, which leads to the appearance of chaotic modes in the cavity and the failure of the single-mode regime.

The second ohmic contact of the first resonator on the WGM is needed to implement a controlled absorber, the fourth ohmic contact of the first resonator on the WGM is used to pump the first resonator, and the third ohmic contact is used to pump the second truncated resonator on the WGM.

The second resonator on the WGM truncated along a plane parallel to its axis, on the side opposite the first resonator, the second ohmic contact in the form of a half ring, the third ohmic contact in the form of a ring part and the fourth ohmic contact in the form of a half ring applied to the end of the first resonator on the WGM, opposite the second ohmic contact, allows the formation of two coherent directional laser beams, reduces the overall quality factor of the resonant system of a semiconductor source, which ensures This increases the output radiation power and wider restructuring of the radiation generation line.

The present invention is illustrated in the drawing, where:

in FIG. 1 shows a side view of a semiconductor infrared source with two optically coupled and jumper-connected whispering gallery (WGM) resonators in the form of a disk and a truncated disk, respectively;

in FIG. 2 is a plan view of the semiconductor infrared source shown in FIG. one;

in FIG. 3 schematically shows a band diagram of a resonator on a WGM of the semiconductor infrared source shown in FIG. 1 (E _c - conduction band, E _v - valence band);

in FIG. 4 shows a side view of a semiconductor infrared radiation source with two resonators coupled and connected by a jumper on the WGM, respectively, in the form of a ring and a truncated ring;

in FIG. 5 is a plan view of the semiconductor infrared source shown in FIG. 6.

The semiconductor source of infrared radiation includes a semiconductor substrate 1, for example, of n-GaAs, InP, A ² B ⁶ , on one side of which are formed, for example (see Fig. 1, Fig. 2), the disk 2 on the WGM and resonator 3 on the WGM in the form of a truncated disk. Resonators on WGM can also be made (Fig. 4, Fig. 5) as follows: resonator 4 on WGM in the form of a ring and resonator 5 on WGM in the form of a truncated ring. Resonators 2, 3, 4 and 5 on WGM are made of semiconductor heterostructures. Resonators 2, 4 include a first restriction layer 6, an active region 7, a second restriction layer 8, as well as half-rings first contact layer 9 and second contact layer 10, second ohmic contact 11 and fourth ohmic contact 12. Resonators 3, 5 include the first limiting layer 6, the active region 7, the second limiting layer 8, as well as the third contact layer 13 and the third ohmic contact 14. The first ohmic contact 15 is applied to the other side of the substrate 1. The distance from the outer edge of the ohm contacts 11, 12, 14 to the outer edge of the resonators 2, 4 and the resonators 3, 5, respectively, does not exceed 100 μm, the Resonators 2, 3, 4 and 5 may, for example, contain (see Fig. 3) the first limiting layer 6 of n-Al _0.9 Ga _0.1 As _0.08 Sb _0.92 , active region 7 of Al _0.25 Ga _0.75 As _0.02 Sb _0.98 with two quantum wells 16 from GaInAsSb, second boundary layer 8 of p-Al _0.9 Ga _0.1 As _0.08 Sb _0.92 and a contact layer, respectively 10 (13) of p-GaSb. Resonators 2, 4 are optically coupled respectively with resonators 3, 5. At least the active regions of resonators 2, 4 are connected by jumpers 17, 18 of length L and width h, respectively, at least with the active regions of resonators 3, 5, respectively. Length L and width h jumpers 17, 18 satisfy the relations:

0 <L <5λ;

0 <h <0.2⋅R.

). Система имела два выходных лазерных пучка, выходящих с боковой поверхности резонатора 3 в местах скола структуры под омическим контактом 14. При подаче напряжения только на омические контакты 11 и 12 наблюдали многомодовый спектр излучения, при этом двух направленных пучков под омическим контактом 14 у резонатора 3 не наблюдали, так как резонатор 3 без подачи напряжения питания работает как поглощающий элемент. Излучение в данном случае выходит только с боковой поверхности резонатора 2. При подаче напряжение только на омический контакт 14 наблюдали многомодовый спектр излучения с двумя направленными лазерными пучками под омическим контактом 14 у резонатора 3.A semiconductor source of infrared radiation operates as follows. When 11, 12, and 14 voltage pulses of rectangular shape (relative to the grounded ohmic contact 15) with a duration of 3–40 μs of a certain frequency (0.5–16 kHz) were applied to the ohmic contacts, the laser system entered the single-mode generation mode. To ensure the tuning of the laser line, the amplitude of the supply pulses at the ohmic contacts 12 and 14 was fixed at the same level (4 V), and at the ohmic contact 11 the voltage was varied over a wide range (0-6 V), while the system generated one mode that could be rebuild over a wide range (up to

) The system had two output laser beams emerging from the side surface of the resonator 3 in the places of cleavage of the structure under the ohmic contact 14. When voltage was applied only to the ohmic contacts 11 and 12, a multimode emission spectrum was observed, while two directed beams under the ohmic contact 14 at the resonator 3 did not observed, since the resonator 3 without supply voltage operates as an absorbing element. The radiation in this case comes only from the side surface of the resonator 2. When applying voltage only to the ohmic contact 14, a multimode emission spectrum with two directed laser beams under the ohmic contact 14 near the resonator 3 was observed.

.Example 1. The semiconductor source of infrared radiation included a semiconductor substrate of n-GaSb, on one side of which were formed in the form of heterostructures: the first resonator on WGM, in the form of a disk and the second resonator on WGM in the form of a half-disk, optically coupled and geometrically connected by a jumper of length L = 10 μm and a width of h = 10 μm over the entire height of the resonators. The first ohmic contact was applied to the other side of the substrate. Resonators on the WGM contained (see FIG. 1, FIG. 2) a first boundary layer of n-Al _0.9 Ga _0.1 As _0.08 Sb _0.92 , an active region of n-Al _0.25 Ga _{0, 75} As _0.02 Sb _0.98 with two quantum wells of n-Ga _0.65 In _0.35 As _0.11 Sb _0.89 , the second boundary layer of p-Al _0.9 Ga _0.1 As _0.08 Sb _0.92 , respectively, contact p-GaSb layers and ohmic contacts Cr-Au: Te-Au. An ohmic contact was applied to the other side of the substrate. Voltage pulses (duration 3–40 μs) with different frequencies (0.5–16 kHz) were applied to the corresponding ohmic contacts of the resonators, as a result of which the resonators began to operate at their own frequency. In this case, the electromagnetic wave circulating in a circle in the waveguide of each of the resonators flowed over the jumper from one resonator to another. Then both resonators began to generate radiation at the same frequency, since the modes closest in frequency to each resonator tuned their frequency and entered the resonance, while the remaining modes were turned off. Thus, a single frequency source of infrared radiation began to work. The output radiation power was higher compared to the prototype semiconductor source. In this case, the tuning of the laser radiation generation line to

.

.Example 2. The semiconductor source of infrared radiation included a semiconductor substrate of n-GaSb, on one side of which were formed in the form of heterostructures (similar to example 1): the first resonator on WGM, in the form of a ring and the second resonator on WGM in the form of a half-ring, optically coupled and geometrically connected by a jumper with a length L = 10 μm and a width h = 10 μm over the entire height of the resonators. In the wavelength range of 2.26-2.27 μm, both resonators entered the resonance and generated coherent radiation at the same frequency. Thus, both resonators worked as a single-frequency infrared emitter, forming two coherent directional laser beams. The output radiation power was higher compared to the prototype semiconductor source. In this case, the tuning of the laser radiation generation line to

.

Claims (9)

1. A semiconductor source of infrared radiation, including a semiconductor substrate with first and second optically coupled whispering gallery (WGM) resonators in the form of heterostructures containing an active region, a first ohmic contact deposited on the surface of the semiconductor substrate, an opposite surface with the first and second resonators on WGM, and the second and third ohmic contacts deposited on the end face of the first and second resonators on WGM, respectively, and the distance from the outer edge of the second and third contact acts to the outer edge of the first and second resonators on the WGM, respectively, does not exceed 100 μm, characterized in that at least the active regions of the first and second resonators on the WGM are connected by a jumper of length L and width h, satisfying the relations: 0 <L <5λ; 0 <h <0.2⋅R; where λ is the radiation wavelength (in air) of the semiconductor source of infrared radiation, microns; R is the radius of the resonator, microns; the second resonator on the WGM from the side opposite the first resonator on the WGM is truncated in a plane parallel to its axis, the second ohmic contact is made in the form of a half ring, the third ohmic contact is made in the form of a part of the ring, and the fourth ohmic contact is applied to the end of the first resonator on the WGM in the form of a half ring opposite to the second ohmic contact. 2. The source according to claim 1, characterized in that the second resonator on the WGM is truncated along the diameter of the resonator. 3. The source according to claim 1, characterized in that the first and second resonators on the WGM are made respectively in the form of a disk and a truncated disk. 4. The source according to claim 1, characterized in that the first and second resonators on the WGM are made respectively in the form of a ring and a truncated ring.

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