Development and research of fiber optics for lasers and amplifiers

The laboratory's primary research focuses on the creation of near-IR lasers and amplifiers based on fiber optics of varying chemical compositions. Detailed spectroscopic studies are conducted on bulk samples and optical fibers doped with rare-earth ions (Yb, Yb-Er, Tm, Nd, etc.), d- and p-elements (Bi, Pb, Te, Cr, etc.). The laboratory has the capability to conduct experiments over a wide temperature range. Much attention is paid to the creation of circuits and laboratory prototypes of fiber-optic devices, in particular, continuous-wave and pulsed lasers, optical amplifiers, and superluminescent radiation sources based on the active fiber optics being developed, as well as fiber optics with nonlinear optical properties. The laboratory also conducts modeling and experimental research into the implementation of high-power laser systems and the search for optimal fiber optic designs for constructing such systems. Over the past two decades, the laboratory has been conducting intensive research into the development of bismuth-doped optical fibers. It is a global leader in this field, having conducted pioneering research into the creation of the first bismuth lasers and amplifiers operating in the 1.25 to 1.77 µm wavelength range.

1. S. A. Ostrikov, A.V. Kharakhordin, K.E. Riumkin, A.S. Lobanov, E.G. Firstova, S.V. Alyshev, A.M. Khegai, A.A. Umnikov, D.S. Lipatov, M.A. Melkumov, S.V. Firstov, Ten-watt fiber laser and high-gain optical amplifier for a wavelength band of 1.2-1.3 µm based on new bismuth active centers //Optics & Laser Technology. – 2026. – vol. 196. – p. 114651.
2. S. Firstov, A. Kharakhordin, S. Ostrikov, A. Lobanov, K. Riumkin, A. Elopov, S. Alyshev, V. Agakhanova, F. Afanasiev, A. Umnikov, E. Firstova, Elena, A. Abramov, A. Khegai, D. Lipatov, M. Melkumov, Hybrid Active Center in Bismuth-Doped AlPO4 -Containing Glass Fibers for T+O-Band Lasers and Amplifiers // Journal of Lightwave Technology. – 2026. doi: 10.1109/JLT.2026.3678729.

1. S. Alyshev, A. Kharakhordin, A. Umnikov, D. Oleinik, A. Khegai, A. Elopov, K. Riumkin, E. Firstova, F. Afanasiev, D. Lipatov, M. Melkumov, S. Firstov, Ultra-broadband optical amplifiers based on bismuth-doped heterogeneous-core fibers // Optics Letters. – 2025. – Vol. 50, N 16. – P. 4918. DOI: 10.1364/OL.567880
2. S.V. Alyshev, A.M. Khegai, A.A. Umnikov, S.V. Firstov, S. V. Multimode LD-pumped bismuth-doped fiber lasers and amplifiers // Optical Fiber Technology. – 2025. – vol. 96. – P. 104503. DOI: 10.1016/j.yofte.2025.104503.
3. Elopov A.V., Riumkin K.E., Alyshev S.V., Kharakhordin A.V., Khegai A.M., Denisov A.N., Firstova E.G., Afanasiev F.V., Abramov A.N., Lipatov D.S., Firstov S.V., Melkumov M.A. Effect of optical anisotropy of bismuth active centers on polarization properties of fiber laser at 1.46 µm // Optics Letters. – 2025. – Vol. 50, No. 19. – P. 6173-6176
4. A.V. Kharakhordin, S.V. Alyshev, A.A. Umnikov, D.I. Oleinik, E.G. Firstova, A.M. Khegai, A.V. Elopov, M.A. Melkumov, S.V. Firstov, Thermally induced transformation of “dark” precursors into laser-active centers: Hidden potential of bismuth-doped fibers // Optical Materials. – 2025. – vol. 164. – P. 117025. DOI: 10.1016/j.optmat.2025.117025
5. A.V. Kharakhordin, A.A. Umnikov, S.V. Alyshev, A.M. Khegai, D.I. Oleinik, A.V. Elopov, D.S. Lipatov, K.E. Riumkin, A.N. Abramov, E.G. Firstova, M.A. Melkumov, S.V. Firstov, Dual-wavelength NIR lasers based on cladding-pumped bismuth-doped heterogeneous fibers // Optical Fiber Technology. – 2025. – Vol. 93. – P. 104277. DOI: 10.1016/j.yofte.2025.104277
6. A. Khegai, S. Firstov, K. Riumkin, D. Lipatov, M. Melkumov, Tm-doped fiber laser cladding pumped by a pulsed Er-doped fiber laser with a 110 μm core // Photonics. – 2025. – Vol. 12, No. 1. – P. 28.
7. K.Y. Lau, J. Lin, S. Firstov, F. Afanasiev, X. Liu, J. Qiu, A low-threshold nonlinear-amplifying-loop-mirror mode-locked bismuth-doped fiber laser using a 3×3 coupler // Journal of Lightwave Technology. –2025. – Vol. 43, no. 1. – P. 328-333. DOI: 10.1109/JLT.2024.3445155.
8. A. Vakhrushev, A. Umnikov, A. Khegai, K. Riumkin, D. Oleinik, A. Abramov, A. Kharakhordin, S. Alyshev, E. Firstova, L. Iskhakova, D. Lipatov, M. Melkumov, S. Firstov, Ultra-wideband amplification in telecom bands with Bi-doped multi-layered glass fibers // J. Lightwave Technology. – 2025. – Vol. 43, Is. 5. – P. 2291 – 2297. DOI: 10.1109/JLT.2024.3491814
9. A.S. Vakhrushev, A.A. Umnikov, D.I. Oleinik, A.M. Khegai, S.V. Alyshev, E.G. Firstova, A.V. Kharakhordin, L.D. Iskhakova, M.A. Melkumov, S.V. Firstov, Watt-level cladding-pumped bismuth-doped fiber laser operating near 1.31 μm // Optics and Laser Technology. – 2025. – Vol. 180. – P. 111526. DOI: 10.1016/j.optlastec.2024.111526.
10. Lin J., Lau K.Y., Firstov S., Afanasiev F., Liu X., Qiu J. A low-threshold nonlinear-amplifying-loop-mirror mode-locked bismuth-doped fiber laser using a 3×3 coupler. // J. Lightwave Technol. – 2025. – Vol. 43. –Is.1 –P.328-333 DOI: 10.1109/JLT.2024.3445155.
11. Vakhrushev A.S., Umnikov A.A., Oleinik D.I., Khegai A.M., Alyshev S.V., Firstova E.G., Kharakhordin A.V., Iskhakova L.D., Melkumov M.A., Firstov S.V. Watt-level cladding-pumped bismuth-doped fiber laser operating at near 1.31 µm. // Optics and Laser Technology. – 2025. – Vol. 180. – 111526. DOI: 10.1016/j.optlastec.2024.111526.

1. Alyshev S., Khegai A., Umnikov A., Firstov S. Bismuth-doped fiber lasers and amplifiers operating from O- to U-band: current state of the art and outlook. // Photonics. – 2024. – Vol. 11, No. 7. – P. 663. DOI: 10.3390/photonics11070663.
2. Alyshev S., Vakhrushev A., Khegai A., Firstova E., Riumkin K., Melkumov M., Iskhakova L., Umnikov A., Firstov S. Impact of doping profiles on the formation of laser-active centers in bismuth-doped GeO₂–SiO₂ glass fibers. // Photonics Research. – 2024. – Vol. 12. – P. 262-270. DOI: 10.1364/PRJ.498782.
3. Alyshev S., Vakhrushev A., Umnikov A., Velmiskin V., Oleinik D., Melkumov M., Semjonov S., Riumkin K., Khegai A., Firstova E., Iskhakova L., Firstov S. Supermode lasing and light amplification in multicore bismuth-doped fiber. // Optics Express. – 2024. – Vol. 32, No. 17. – P. 29214-29226. DOI: 10.1364/OE.531655.
4. Elopov A.V., Riumkin K.E., Afanasiev F.V., Alyshev S.V., Kharakhordin A.V., Khegai A.M., Firstov S.V., Melkumov M.A. Polarization dependent gain in bismuth-doped phospho- and germanosilicate fiber amplifiers. // Opt. Lett. –2024. – Vol. 49, No. 18. – P. 5300-5303. DOI: 10.1364/OL.532968.
5. Hu J., Wang Y., Lau K.Y., Han X., Firstov S., Zhong L., Qiu J. Suppressing side-scattering on laser-written Bragg gratings for back-reflection engineering in fibers. // Laser and Photonics Reviews –2024. – Vol. 18. – 2400303. DOI: 10.1002/lpor.202400303
6. Lau K., Firstov S., Luo Z., Hu M., Senatorov A., Umnikov A., Xu B., Liu X., Qiu J. 1450 nm high energy noisy multi-pulse mode-locking in bismuth-doped fiber laser. // J. Lightwave Technol. –2024. – Vol. 42. – P. 2103-2110. DOI: 10.1109/JLT.2023.3331983
7. Lau K., Firstov S., Luo Z., Senatorov A., Umnikov A., Liu X., Qiu J. E-band domain-wall dark-pulsed bismuth-doped fiber laser // Journal of Luminescence. – 2024. – Vol. 269. – P. 120485. DOI: 10.1016/j.jlumin.2024.120485
8. Vakhrushev A., Umnikov A., Dostovalov A, Riumkin K., Alyshev S., Firstova E., Khegai A., Melkumov M., Babin S., Firstov S. Cladding-pumped laser and amplifier for E- and S-bands based on multimode bismuth-doped graded-index fibers: toward watt-level output power. // Opt. Lett. – 2024. – Vol. 49. – P. 1828. DOI: 10.1364/OL.514236
9. Wang Hang, Song Luming, Chen Tingting, Huang Lu, Han Fengbo, Chen Huaixi, Dong Zhipeng, Bu Yikun, Melkumov Mikhail, Firstov Sergei, Lobanov Alexey, Luo Zhengqian. 1283-1460 nm continuously-tunable, watt-level bismuth-doped phosphosilicate fber laser and its frequency doubling to visible laser. // Opt. Lett. – 2024. – Vol. 49, Issue 15. – P. 4062-4065. DOI: 10.1364/OL.522896.
10. Wang Y., Zhong L., Lau K.Y., Han X., Yang Y., Hu J., Firstov S., Chen Z., Ma Z., Tong L., Seng Chiang K., Tan D., Qiu J. Precise mode control of laser-written waveguides for broadband, low-dispersion 3D integrated optics. // Light: Science & Applications. – 2024. – Vol. 13. – P. 130. DOI: 10.1038/s41377-024-01473-7.

1. Wang H., Yang Y., Hong J., Zhou X., Ruan Q., Dong Z., Melkumov M., Firstov S., Lobanov A., Luo Z. 1.3/1.4 µm dual-wave band dissipative soliton resonance in a passively mode-locked Bi-doped phosphosilicate fiber laser. // Optics Letters. – 2023. – V. 48, N. 2. – P.299-302. DOI: 10.1364/OL.480137.
2. Mkrtchyan A. A., Mishevsky M. S., Gladush Y. G., Melkumov M. A., Khegai A. M., Lagoudakis P. G., Nasibulin A. G. Dispersion Managed Mode-locking in all-fiber Polarization-maintaining Nd-doped Laser at 920 nm. // Journal of Lightwave Technology. – 2023. – V. 41, N. 8. – P.2494-2500. DOI: 10.1109/JLT.2022.3229826.
3. Vakhrushev A., Khegai A., Alyshev S., Riumkin K., Kharakhordin A., Firstova E., Umnikov A., Lobanov A., Afanasiev F., Guryanov A., Firstov S. Cladding pumped bismuth-doped fiber amplifiers operating in O-, E-, and S-telecom bands. // Optics Letters. – 2023. – V. 48, N. 6. – P.1339-1342. DOI: 10.1364/OL.482873
4. Wang Wang H., Jia W., Yao Y., Yang X., Melkumov M., Firstov S., Lobanov A., Dong Z., Luo Z., Generation of 1.3/1.4 µm random fiber laser by bismuth-doped phosphosilicate fiber // Chin. Opt. Lett. – 2023. – V. 21 – P. 071401. DOI: 10.3788/COL202321.071401
Kharakhordin A., Rybaltovsky A., Popov S., Ryakhovskiy D., Afanasiev F., Alyshev S., Khegai A., Melkumov M., Firstova E., Chamorovsky Y., Umnikov A., Lipatov D., Firstov S. Random laser operating at near 1.67 μm based on bismuth-doped artificial rayleigh Fiber. // Journal of Lightwave Technology. – 2023. – V. 41, N. 19. – P. 6362-6368. DOI: 10.1109/JLT.2023.3285041.
5. Vakhrushev A.S., Alyshev S.V., Khegai A.M., Firstova E.G., Kharakhordin A.V., Riumkin K.E., Melkumov M.A., Umnikov A.A., Afanas’ev F.V., Gur’yanov A.N., Firstov S.V. Continuous-wave Bismuth-doped Fiber Lasers with Multimode Diode Pumping. // Optoelectronics, Instrumentation and Data Processing. – 2023. – V. 59, N. 1. – P. 1-9. DOI:10.3103/S8756699023010120.
6. Lau K. Y., Firstov S., Cui Y., Liu X., Afanasiev F. and Qiu J. Highly efficient O-band rectangular pulse emission in a figure-of-nine bismuth-doped fiber laser. // Journal of Lightwave Technology. – 2023 – V. 41, N. 19. P. – P. 6383-6388. DOI: 10.1109/JLT.2023.3284132.
7. Elopov A. V., Riumkin K. E., Afanasiev F. V., Alyshev S. V., Kharakhordin A. V., Khegai A. M., Firstova E.G., Firstov S.V., Nishchev K.N., Melkumov M. A. Polarized Luminescence of Bismuth Active Centers in Phosphosilicate Glasses. // Photonics. – MDPI. – 2023 – V. 10, N. 8. – P. 860. DOI: 10.3390/photonics10080860.

• For the first time in the world, bismuth-doped glass matrices have been proposed and developed as the basis for fiber optic cores. These matrices have enabled the formation of bismuth active centers (BACs) with optical transitions in previously inaccessible spectral regions, namely, 1280–1775 nm. The relationship between the spectral positions of the maxima and the shapes of the optical gain bands, the absorption bands, and the chemical composition of bismuth-doped glass has been established. A classification of bismuth active center (BAC) varieties has been developed for the first time and is used by the global scientific community.


• For the first time, an energy level diagram has been determined for three types of BACs: BACs associated with P, Si, and Ge atoms. The main radiative and absorption transitions characteristic of such BACs have been identified. It was established that the studied BACs have similar level structure structures, with the main difference being the difference in energy level arrangement: each level in the Ge and P BACs is 10-16% lower and higher in energy than the same level in the Si BAC, respectively.


• For the first time in the world, a family of bismuth fiber lasers operating in continuous mode over a wide range of the near-IR spectrum (1280–1775 nm) has been created based on the developed bismuth fiber optics. Record-breaking efficiency values ​​of 30–80% and laser output power of 10–20 W have been achieved. The feasibility of achieving tunable laser generation over a wide spectral range using various types of BACs has been demonstrated.


• The first efficient optical signal amplifiers for the 1320 nm (FWHM = 37 nm), 1430 nm (FWHM = 34 nm), and 1700 nm (FWHM = 40 nm) wavelength ranges were created using bismuth-doped optical fibers. The signal-to-noise ratio of the bismuth amplifiers was 4-6 dB. The maximum achieved efficiency of bismuth amplifiers is 60%, a record-breaking achievement to date.


• A concept for smoothly controlling the optical properties of bismuth-doped optical fibers using a W-structure (the core of such a fiber is surrounded by glass with a lower refractive index than quartz glass) was proposed. This enabled the creation of a series of active media with specified optical parameters and low macrobending losses. A compact and efficient bismuth-doped amplifier for the 1.28-1.35 µm spectral range (in the O-band) was developed using this type of fiber. This compact design was achieved by allowing the active fiber to be wound onto a 3-cm diameter spool. This amplifier demonstrated record-breaking efficiency in converting pump radiation into a signal. Furthermore, this approach was used to create a bismuth fiber with an extremely low phosphorus oxide content (<2 mol.% without distorting the parameters of the fiber structure), which enabled comparable concentrations of various types of bismuth active centers associated with Si and P atoms in the core. The result was an active medium with a broad optical gain profile due to the strong overlap of the gain bands of these active centers.


• An ultra-wideband amplifier for the 1520-1775 nm spectral range based on a high-germanate fiber co-doped with erbium and bismuth has been proposed and implemented for the first time.
  Patent No. 2627547 RU


• The phenomenon of photobleaching occurring in bismuth-doped fibers upon irradiation with laser radiation in the UV, visible, and IR ranges has been discovered and studied. Dynamic and spectral dependences of changes in the absorption and luminescence band intensities for BACs during laser irradiation have been obtained. It is shown that the photobleaching process is due to photobleaching of the BAC. A detailed analysis of the specific features of the BAC photobleaching process is performed, which leads to the proposed mechanism for this phenomenon, which involves modification of the local structure of the active center due to photoionization of an oxygen-deficient defect. Furthermore, a theoretical study of the effect of pump radiation, i.e., the possible contribution to the photobleaching process, on the output characteristics of bismuth fiber lasers was performed. This allowed us to construct a phenomenological model of BAC bleaching upon irradiation with IR radiation under various temperature conditions.


• Development of the world's first cladding-pumped bismuth fiber laser, operating at a wavelength of 1460 nm. The operating characteristics of this laser were studied. The possibility of scaling the output power of such lasers above 1 W was demonstrated.


• The effect of thermally induced formation of active centers in bismuth-doped light guides has been discovered. Fundamental research has been conducted to study in depth the physicochemical processes of active center formation during heat treatment of bismuth-doped light guides. Characteristic parameters of these processes have been determined, and a mechanism for the processes involved has been proposed.


• An original approach has been proposed for assessing the potential of bismuth-doped light guides. This approach is based on a comprehensive study of "dark" precursors—forms undetectable by IR absorption and luminescence spectroscopy—that can be transformed into active bismuth centers (BACs) through thermally induced processes in a germanosilicate glass matrix with an activation energy of ~2.1 eV. Using the demarcation energy method within this approach, it was found that bismuth-doped fibers exhibit varying levels of "latent" potential, expressed as the fraction of bismuth ions converted to BACs. Specifically, it was found that the best fibers of this type can achieve Bi → BAC conversion of up to ~90%, leading to an increase in the linear gain of the active medium and the development of optical devices with record-breaking performance. It was found that with increasing bismuth concentration and changing process conditions, the Bi → BAC conversion rate significantly decreased to 50%, accompanied by an increase (~30%) in the amount of inactive Bi species responsible for non-saturable losses. Thus, the proposed approach enables the evaluation of the properties of bismuth-doped fibers taking into account their "latent" potential, which can be used to find optimal fiber fabrication methods for high-performance fiber lasers and amplifiers.


• An ultra-wideband optical amplifier for the 1260–1480 nm spectral range has been developed and demonstrated using a cladding-pumped bismuth fiber with a heterogeneous core formed by a combination of glass layers containing P2O5 and GeO2. This core structure provides a favorable local environment for the efficient formation of bismuth active centers (BACs) bound to P and Si atoms. This amplifier, pumped into the cladding by multimode laser diodes operating at wavelengths of 793 and 808 nm, is characterized by a peak gain of ≈24 dB, a minimum noise figure of ≈6 dB, and a bandwidth of ≈160 nm at a gain level of 20 dB. The obtained result demonstrates the high potential of using bismuth-doped fiber amplifiers, including cladding-pumped ones, to expand the transmission range of promising high-speed fiber-optic communication lines.


• An approach for scaling the power of all-bismuth fiber lasers built with low-gain active media has been proposed and implemented. This approach is based on the use of multi-core optical fibers (MCFs) with strong mode coupling (supermodes) propagating in different cores. Based on numerical simulations, a conceptual design of such a MCF was proposed and fabricated using a stack-and-draw assembly method using bismuth-doped germanosilicate glasses. The light-guiding, absorption, and luminescence properties of the resulting MCF were studied. It has been experimentally demonstrated that this MCS, when pumped into the cladding using 808 nm multimode laser diodes, is capable of providing 20 dB light gain and stable laser generation in the 1400–1500 nm wavelength range due to intracavity supermode selection. Analysis of experimental and calculated data revealed that the proposed bismuth-doped fiber design offers significant advantages over single-core fiber designs in terms of laser performance (output power, slope efficiency) in a cladding-pumped configuration. These results open up new possibilities for the further development of optical fiber technology in the direction of constructing efficient amplifiers and lasers based on bismuth-doped optical fibers for the O+E+S+C+L+U telecommunication wavelength ranges (1260–1675 nm), which are in high demand, especially for multi-band optical data transmission systems.

1. Moscow Government Prize for Young Scientists (2023) (A.M. Khegay, K.E. Ryumkin, S.V. Firstov)
2. V.S. Letokhov Medal for Young Scientists of the D.S. Lenin Optical Society Rozhdestvensky (2017) (S.V. Firstov)
3. RAS Medal with a Prize for Young Scientists for the series of papers "Development of Efficient Bismuth Fiber Lasers and Amplifiers for the 1280-1775 nm Spectral Range" (2014) (S.V. Firstov)