INVESTIGATION OF FAR-FIELD PATTERNS OF SEMICONDUCTOR MICROLASERS WITH AN ACTIVE REGION BASED ON INGAAS/GAAS QUANTUM WELL-DOTS

Moiseev E.I.; Kryzhanovskaya N.V.; Zubov F.I.; Nahorny A.V.; Urmanov B.D.; Fominykh N.A.; Ivanov K.A.; Mintairov S.A.; Kalyuzhnyy N.A.; Kulagina M.M.; Maximov M.V.; Zhukov A.E.

Conference materials UDC 538.958

DOI: https://doi.org/10.18721/JPM.153.204

Investigation of far-field patterns of semiconductor microlasers with an active region based on InGaAs/GaAs quantum well-dots

E. I. Moiseev 1H, N. V. Kryzhanovskaya \ F. I. Zubov 2, A. V. Nahorny 3, B. D. Urmanov 3, N. A. Fominykh ', K. A. Ivanov ', S. A. Mintairov 4, N. A. Kalyuzhnyy 4, M. M. Kulagina 4, M. V. Maximov 2, A. E. Zhukov 1

1 HSE University, St Petersburg, Russia;

2 Alferov University, St Petersburg, Russia;

3 Institute of Physics of NAS of Belarus, Minsk, Belarus;

4 Ioffe Institute, St Petersburg, Russia H [email protected]

Abstract. This paper is the first study of the far-field patterns of semiconductor microlasers with an active region based on In04Ga06As/GaAs quantum well-dots. A theoretical model describing the far-field radiation pattern is developed. It is shown that in the vertical direction the radiation pattern has a narrow beam divergence (the most of the power is confined to 20 degrees) and is characterized by narrow lobes, the position and number of which are determined by the height of the waveguide relative to the substrate. It is found that in the horizontal direction, each optical mode has its own far-field pattern. A change in the injection current leads to a change in the dominant optical mode and in the far-field pattern. Deviation of the resonator shape from the circular one leads to chaotization of the peripheral modes and generation through more profound WGM-like modes. Reducing the diameter of the resonator leads to a reduction in the number of lobes of the horizontal radiation pattern.

Keywords: Microlaser, quantum dots, radiation pattern, directional output, emission field control, far-field emission

Funding: The study of the far fields was funded by RFBR and BRFBR project number 20-52-04016, the development and modeling of the epitaxial structure are supported by the Basic Research Program at the National Research University Higher School of Economics (HSE University), mounting and soldering of samples are supported by the Ministry of Science and Higher Education of the Russian Federation under project #0791-2020-0002.

Citation: Moiseev E. I., Kryzhanovskaya N. V., Zubov F. I., Nahorny A. V., Urmanov B. D., Fominykh N.A., Ivanov K. A., Mintairov S. A., Kalyuzhnyy N. A., Kulagina M. M., Maximov M. V., Zhukov A. E., Investigation of far-field patterns of semiconductor microlasers with an active region based on InGaAs/GaAs quantum well-dots, St. Petersburg State Polytechnical University Journal. Physics and Mathematics. 15 (3.2) (2022) 25-30. DOI: https://doi.org/10.18721/JPM.153.204

This is an open access article under the CC BY-NC 4.0 license (https://creativecommons. org/licenses/by-nc/4.0/)

Материалы конференции УДК 538.958

DOI: https://doi.org/10.18721/JPM.153.204

Исследование картин дальнего поля полупроводниковых микролазеров с активной областью на основе квантовых ям-точек InGaAs/GaAs

Э. И. Моисеев 1 н, Н. В. Крыжановская ', Ф. И. Зубов 2, А. В. Нагорный 3, Б. Д.

Урманов 3, Н. А. Фоминых 1, К. А. Иванов 1, С. А. Минтаиров 4, Н. А. Калюжный 4, М. М. Кулагина 4, М. В. Максимов 2, А. Е. Жуков 1

1 НИУ ВШЭ, Санкт-Петербург, Россия;

© Moiseev E. I., Kryzhanovskaya N. V., Zubov F. I., Nahorny A. V., Urmanov B. D., Fominykh N.A., Ivanov K. A., Mintairov S. A., Kalyuzhnyy N. A., Kulagina M. M., Maximov M. V., Zhukov A. E., 2022. Published by Peter the Great St.Petersburg Polytechnic University.

2 Алферовский университет, Санкт-Петербург, Россия;

3 Институт физики НАН Беларуси, Минск, Белоруссия;

4 ФТИ им. А.Ф. Иоффе, Санкт-Петербург, Россия и [email protected]

Аннотация. В работе впервые проведено исследование картин дальнего поля полупроводниковых микролазеров с активной областью на основе квантовых ям-точек In0 4GaQ gAs/GaAs. Разработана теоретическая модель, описывающая картину излучения в дальней зоне. Показано, что в вертикальном направлении диаграмма направленности имеет узконаправленный характер (основная часть мощности ограничивается в диапазоне 20 градусов) и характеризуется узкими лепестками направленности, положение и количество которых определяется высотой волновода относительно подложки. Установлено, что в горизонтальном направлении каждой оптической моде соответствует своя картина дальнего поля. Изменение тока накачки приводит к смене доминантной оптической моды и картины дальнего поля. Отклонение формы резонатора от круговой приводит к хаотизации периферийных мод и генерации через более углубленные МШГ-подобные. Уменьшение диаметра резонатора позволяет уменьшить количество лепестков горизонтальной диаграммы направленности.

Ключевые слова: микролазер, квантовые точки, диаграмма направленности, направленный вывод излучения, управление полями излучения, дальнее поле излучения

Финансирование: Исследование дальних полей выполнено при финансовой поддержке РФФИ в рамках научного проекта № 20-52-04016, разработка и моделирование эпитаксиальной структуры выполнены при поддержке Программы фундаментальных исследований НИУ ВШЭ, монтаж и пайка приборов выполнены при поддержке Министерством науки и высшего образования Российской Федерации по проекту № 0791-2020-0002.

Ссылка при цитировании: Моисеев Э. И., Крыжановская Н. В., Зубов Ф. И., Нагорный А. В., Урманов Б. Д., Фоминых Н. А., Иванов К. А., Минтаиров С. А., Калюжный Н. А., Кулагина М. М., Максимов М. В., Жуков А. Е. Исследование картин дальнего поля полупроводниковых микролазеров с активной областью на основе квантовых ям-точек InGaAs/GaAs // Научно-технические ведомости СПбГПУ. Физико-математические науки. 2022. Т. 15. № 3.2. С. 25-30. DOI: https://doi.org/10.18721/ JPM.153.204

Статья открытого доступа, распространяемая по лицензии CC BY-NC 4.0 (https:// creativecommons.org/licenses/by-nc/4.0/)

Introduction

Semiconductor microlasers with a resonator supporting whispering gallery modes (WGM) are considered as promising elements for implementation of optical communication systems on a chip, detectors and biosensors with extremely high sensitivity [1], [2] and for fundamental research in quantum electrodynamics, in particular, realization of a strong coupling regime [3], open chaotic systems [4] and non-hermitian quantum mechanics [5].

Recently, results have been presented for microdisk lasers with an active region based on In0 4Ga0 6As/GaAs quantum well-dots (QWDs) [6] which demonstrate high output power of optical emission [7], the possibility of laser generation at elevated temperatures and optical data transmission with a speed up to 10 Gbit/sec [8]. The rotational symmetry of the resonator should lead to isotropic emission of radiation into free space. However, the spectral-angular dependences of the emission intensity in the far field are much more complicated as shown in this work.

Materials and Methods

An epitaxial structure was grown by the MOCVD method on an n-doped GaAs (100) substrate. The active region represents 5 layers of InGaAs QWDs separated with 40 nm thick GaAs spacers. The active region was deposited in the middle of a 0.8 ^m thick GaAs waveguide layer confined

© Моисеев Э. И., Крыжановская Н. В., Зубов Ф. И., Нагорный А. В., Урманов Б. Д., Фоминых Н. А., Иванов К. А., Минтаиров С. А., Калюжный Н. А., Кулагина М. М., Максимов М. В., Жуков А. Е., 2022. Издатель: Санкт-Петербургский политехнический университет Петра Великого.

from both sides with AlGaAs claddings. Microdisk resonators with a height of about 5.5 ^m and diameters of 30, 50, 100 and 200 ^m were formed using photolithography and plasma chemical etching. AgMn/NiAu (AuGe/Ni/Au) metallization was used to form ohmic contacts to p+ GaAs cap layer (n+ substrate, respectively).

The GaAs wafer with microlasers was split into separate chips with single microlasers. The chips with microlasers were mounted on a heat sink. A 17.5 ^m diameter gold wire was used to electrically connect the microlaser to the contact pad (Fig. 1, a). A stabilized Keithley 2400 source was used for current pumping of the structures. The spectral-angle patterns of the far field were measured on a specialized automatic stand. The electroluminescence emission was injected into the optical fiber through an adapter. The collimator aperture was limited by an aperture to control the angular resolution (0.3°). The measurements were performed at room temperature and CW mode.

Results and Discussion

The electroluminescence spectra of the microlasers contain narrow lines and a wide band corresponding to the spontaneous emission of the In04Ga06As/GaAs active region. With an increase in the pump current, the onset of lasing is observed (Fig. 1, b).

Fig. 1. Image of a heat sink-mounted chip with a 100 ^m microlaser (a); electroluminescence spectra of a 50 ^m microlaser below and above the threshold current (Ith = 20 mA) (b); inset: integrated line

intensity as a function of pump current

Figure 2, a shows the angular distribution of the field intensity in the polar angle (in vertical direction) below and above the threshold current. The dependences show that the light is primarily emitted in the lateral direction and has an intensity modulation both below and above the threshold current.

Modeling of the vertical radiation pattern showed that changing the height of the active region relative to the surface of the substrate leads to a change in the number and position of the lobes of the radiation pattern (Fig. 2, b) and is caused by interference of radiation coming from the waveguide with radiation reflected from the surface of the substrate. In this case, the narrow-directional type of the vertical radiation pattern is retained, and the main part of the power is limited in the angular range of 20 degrees.

The horizontal (in-plane) radiation pattern below the threshold current is isotropic. However, above the threshold current includes modulation of the emission intensity (Fig. 3 a, b). The number of lobes of the radiation pattern increases as the diameter of the resonator increases. The experimentally observed number of peaks turns out to be much smaller than the number of the intensity maxima expected for the whispering gallery mode of the lowest radial order. For example, for a microlaser with a diameter of 30 ^m, 144 maxima of intensity are observed, while about 600 are expected. This discrepancy is probably due to the effect of frequency synchronization of spatial modes [9]-[11] and the formation of non-classical WGM in a resonator with a nonideal form [12]-[13]. Numerical simulations of far-field patterns for Lima9on-shaped microlasers show that deviation of the resonator shape from the ideal (axially symmetric) one can lead to

Fig. 2. Vertical directional pattern at different pump currents (a) and different heights of the active region relative to the substrate — model (solid lines) and experiment (dotted line) (b)

chaotization of peripheral modes and formation of WGM-like modes, which are characterized by a smaller number of directional lobes.

It was found that each optical mode corresponds to a different far-field pattern. For a microlaser with a resonator diameter of 50 ^m, when the pump current is increased from 30 to 49 mA, a spectral long-wavelength shift of the laser line (Xj) occurs due to heating of the structure. In this case, the position of the lobes of the radiation pattern does not change (Fig. 3 c, d). At a pump current of 51 mA, the dominant mode is changed (from Xj to X2), which leads to a change in the position of the lobes of the horizontal radiation pattern.

a)

c)

¡(¡I

s

S 1E-7

43 mA

A *

■ieùmji.

b)

1 t> ' -1Î ^D ' j -ID D "— dB

r\ L y "M M im '

Ï -¡u J ,' ' g ', '

V V

' - v -/ \

\

30

P(«eg>

Fig. 3. Horizontal radiation pattern for a 50 ^m microlaser (a) and results for structures with 30, 50, and 100 ^m resonator diameters (b); electroluminescence spectra (c) and horizontal radiation pattern at different pump currents (d)

Conclusion

In this work, we studied, for the first time, the far-field patterns of semiconductor microlasers with an active region based on In0 4Ga0 gAs/GaAs quantum well-dots. A theoretical model describing the far-field radiation pattern is developed. It is shown that in the vertical direction the radiation pattern has a narrow directionality (the main part of the power is confined to 20 degrees) and is characterized by narrow lobes, the position and number of which are determined by the height of the waveguide relative to the substrate, which is determined during the fabrication of the structures.

It was found that in the horizontal direction, each optical mode corresponds to a different far-field pattern. A change in the pump current leads to a change in the dominant optical mode and the far-field pattern. Deviation of the resonator shape from the circular leads to chaotization of the peripheral modes and generation through more profound WGM-like, which are characterized by a smaller number of directional lobes. Reducing the diameter of the resonator leads to a decrease in the number of lobes of the horizontal radiation pattern.

REFERENCES

1. He L., Özdemir §.K., Zhu J., Kim W., Yang L., Detecting single viruses and nanoparticles using whispering gallery microlasers // Nature Nanotechnology. 2011. № 7(6). C. 428-432. D01:10.1038/ nnano.2011.99.

2. Toropov N., Cabello G., Serrano M.P., Gutha R.R., Rafti M., Vollmer F., Review of biosensing with whispering-gallery mode lasers // Light: Science & Applications. 2021. № 1(10). C. 42. D0I:10.1038/ s41377-021-00471-3.

3. Gayral B., Gérard J.-M., Sermage B., Lemaitre A., Dupuis C., Time-resolved probing of the Purcell effect for InAs quantum boxes in GaAs microdisks // Applied Physics Letters. 2001. № 19(78). C. 2828-2830.

4. Nöckel J.U., Stone A.D., Ray and wave chaos in asymmetric resonant optical cavities // Nature. 1997. № 6611(385). C. 45-47. D0I:10.1038/385045a0.

5. Lee S.-B., Yang J., Moon S., Lee S.-Y., Shim J.-B., Kim S.W., Lee J.-H., An K., Observation of an Exceptional Point in a Chaotic Optical Microcavity // Physical Review Letters. 2009. № 13(103). C. 134101. D0I:10.1103/PhysRevLett.103.134101.

6. Maximov M.V., Nadtochiy A.M., Mintairov S.A., Kalyuzhnyy N.A., Kryzhanovskaya N.V., Moiseev E.I., Gordeev N.Y., Shernyakov Y.M., Payusov A.S., Zubov F.I., Nevedomskiy V.N., Rouvimov S.S., Zhukov A.E., Light Emitting Devices Based on Quantum Well-Dots // Applied Sciences. 2020. № 3(10). C. 1038. D0I:10.3390/app10031038.

7. Moiseev E., Kryzhanovskaya N., Maximov M., Zubov F., Nadtochiy A., Kulagina M., Zadiranov Y., Kalyuzhnyy N., Mintairov S., Zhukov A., Highly efficient injection microdisk lasers based on quantum well-dots // 0ptics Letters. 2018. № 19(43). C. 4554. D0I:10.1364/0L.43.004554.

8. Zubov F., Maximov M., Kryzhanovskaya N., Moiseev E., Muretova M., Mozharov A., Kaluzhnyy N., Mintairov S., Kulagina M., Ledentsov N., Chorchos L., Ledentsov N., Zhukov A., High speed data transmission using directly modulated microdisk lasers based on InGaAs/GaAs quantum well-dots // 0ptics Letters. 2019. № 22(44). C. 5442. D0I:10.1364/0L.44.005442.

9. Choi M., Shinohara S., Harayama T., Dependence of far-field characteristics on the number of lasing modes in stadium-shaped InGaAsP microlasers // 0ptics Express. 2008. № 22(16). C. 17554. D0I:10.1364/oe.16.017554.

10. Harayama T., Sunada S., Ikeda K.S., Theory of two-dimensional microcavity lasers // Physical Review A. 2005. № 1(72). C. 013803. D0I:10.1103/PhysRevA.72.013803.

11. Kryzhanovskaya N. V., Zhukov A.E., Nadtochy A.M., Maximov M. V., Moiseev E.I., Kulagina M.M., Savelev A. V., Arakcheeva E.M., Lipovskii A.A., Zubov F.I., Kapsalis A., Mesaritakis C., Syvridis D., Mintairov A., Livshits D., Room-temperature lasing in microring cavities with an InAs/ InGaAs quantum-dot active region // Semiconductors. 2013. № 10(47). C. 1387-1390. D0I:10.1134/ S1063782613100187.

12. Song Q., Fang W., Liu B., Ho S.-T., Solomon G.S., Cao H., Chaotic microcavity laser with high quality factor and unidirectional output // Physical Review A. 2009. № 4(80). C. 041807. D0I:10.1103/ PhysRevA.80.041807.

13. Alekseev P.A., Dunaevskiy M.S., Monakhov A.M., Dudelev V. V., Sokolovskii G.S., Arinero R., Teissier R., Baranov A.N., Half-disk laser: insight into the internal mode structure of laser resonators // 0ptics Express. 2018. № 11(26). C. 14433. D0I:10.1364/0E.26.014433.

THE AUTHORS

MOISEEV Eduard I.

[email protected]

0RCID: 0000-0003-3686-935X

KRYZHANOVSKAYA Natalia V.

[email protected] 0RCID: 0000-0002-4945-9803

ZHUKOV Alexey E.

[email protected]

0RCID: 0000-0002-4579-0718

MAXIMOV Mikhail V.

[email protected] 0RCID: 0000-0002-9251-226X

ZUBOV Fedor I.