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Journal of Experimental and Theoretical Physics Letters

Solid-State Continuous Superradiant Laser with a Wavelength in the Telecommunication Range

K. I. Gerasimov, Mansur M. Minnegaliev, Sergey A. Moiseev

Published Aug 1, 2026• 0 citations
Publisher

Abstract

Superradiance or superfluorescence properties are typically studied under pulsed excitation. In this work, superradiance lasing under continuous pumping without a special external cavity has been studied. Lasing has been achieved in a YPO 4 :Er 3+ solid with a narrow emission line (~48 kHz), in single-mode, single-frequency operation, with a high quantum differential efficiency (~84%), a low lasing threshold, and at a telecommunication wavelength (~1.5 μm).

DOI
10.1134/s0021364026607566

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Superradiance or superfluorescence properties are typically studied under pulsed excitation. In this work, superradiance lasing under continuous pumping without a special external cavity has been studied. Lasing has been achieved in a YPO 4 :Er 3+ solid with a narrow emission line (~48 kHz), in single-mode, single-frequency operation, with a high quantum differential efficiency (~84%), a low lasing threshold, and at a telecommunication wavelength (~1.5 μm).
Sub-Natural Linewidth Superradiant Lasing with Cold 88^{88}88Sr Atoms
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Superradiant lasers operate in the bad-cavity regime, where the phase coherence is stored in the spin state of an atomic medium rather than in the intracavity electric field. Such lasers use collective effects to sustain lasing and could potentially reach considerably lower linewidths than a conventional laser. Here, we investigate the properties of superradiant lasing in an ensemble of ultracold ^{88}Sr atoms inside an optical cavity. We extend the superradiant emission on the 7.5 kHz wide ^{3}P_{1}→^{1}S_{0} intercombination line to several milliseconds, and observe steady parameters suitable for emulating the performance of a continuous superradiant laser by fine tuning the repumping rates. We reach a lasing linewidth of 820 Hz for 1.1 ms of lasing, nearly an order of magnitude lower than the natural linewidth.
We predict collective free-space lasing in a dense nanoscopic emitter arrangement where dipole-dipole coupled atomic emitters synchronize their emission and exhibit lasing behavior without the need for an optical resonator. At the example of a subwavelength-spaced linear emitter chain with varying fractions of pumped and unpumped emitters, we present a comprehensive study of this mirrorless lasing phenomenon. The total radiated power transitions from subradiant suppression under weak pumping to superradiant enhancement at stronger pumping, while exhibiting directional emission confined to a narrow spatial angle. At the same time multiple independent spectral emission lines below the lasing threshold merge toward a single narrow spectral line at high pump power. The most substantial enhancement and line narrowing occur when a fraction of unpumped atoms is present. We show that this leads to superradiant lasing near the bare atomic frequency, making the system a promising candidate for a minimalist active optical frequency reference.
Continuous superradiance using a narrow optical transition has the potential to improve the short-term stability of state-of-the-art optical clocks. Even though pulsed superradiant emission on a mHz linewidth clock transition has been shown, true continuous operation, without Fourier limitation, has turned out to be extremely challenging. The trade-off between maintaining a high atomic flux while minimizing decoherence effects presents a significant obstacle. Here, we discuss the design of a machine that could overcome this problem by combining a high-flux continuous beam of ultracold strontium atoms with a bowtie cavity for the generation of superradiant lasing. To evaluate the feasibility of our design, we present simulation results for continuous high-efficiency cooling, loading, and pumping to the upper lasing state inside the bowtie cavity. We then present two different models for simulating the generated superradiant field by taking into account position-dependent shifts, collisional decoherence, light shifts, and atom loss. Finally, we estimate a laser linewidth of less than 100 mHz , limited by atom number fluctuations, resulting in an output power of hundreds of fW .
Population inversion on the 7S1/2− 6P3/2transition of cesium atoms is built by 455 nm diode laser pumping, and continuous-wave (cw) lasing is observed without the feedback on the gain medium from cavity mirrors. The stimulated emission at 1.47 µm infrared wavelength is restricted to a narrow angle along the direction of propagation of the pumping laser. Evidence of threshold-like characteristic is demonstrated in the cw mirrorless lasing dependence on pumping laser detuning, atomic density, and pumping light intensity. This compact structure can be used to generate mirrorless laser in a number of infrared wavelengths applied for the communication area. Moreover, it is expected to realize the narrow-linewidth optical frequency standard from an ultralow-finesse optical cavity.