Atmospheric conditions such as fog, humidity, and scattering by foliage routinely degrade optical free-space (FS) links, motivating alternatives that are robust in adverse conditions. Coherent microwave sources offer a compelling alternative for quantum-secure communication, yet their propagation outside enclosed resonators has remained untested. Here, we demonstrate room-temperature FS transmission of maser signals generated using organic L-band (1-2 GHz) gain media, pentacene doped p-terphenyl (Pc: PTP), and Diazapentacene-doped p-terphenyl (DAP:PTP). Spectral and temporal coherence is preserved over distances up to 25 cm, approximately one wavelength at the masing frequency. Tests included polarisation misalignment, high-humidity conditions, and partial occlusion by foliage to emulate realistic FS reception scenarios. Strong spin-photon coupling was maintained, as confirmed by persistent rabi oscillations and normal-mode splitting. An instantaneous peak output of 4.29 mW (+6.32 dBm) from a 0.01% DAP:PTP gain medium. with a pulse duration of ~4 μs, marks a performance benchmark for directly coupled masers. These findings demonstrate a proof-of-concept for masers as viable platforms for short-range, interference-resilient coherent microwave links, with future relevance to quantum sensing and secure communication technologies.
Atmospheric conditions such as fog, humidity, and scattering by foliage routinely degrade optical free-space (FS) links, motivating alternatives that are robust in adverse conditions. Coherent microwave sources offer a compelling alternative for quantum-secure communication, yet their propagation outside enclosed resonators has remained untested. Here, we demonstrate room-temperature FS transmission of maser signals generated using organic L-band (1-2 GHz) gain media, pentacene doped p-terphenyl (Pc: PTP), and Diazapentacene-doped p-terphenyl (DAP:PTP). Spectral and temporal coherence is preserved over distances up to 25 cm, approximately one wavelength at the masing frequency. Tests included polarisation misalignment, high-humidity conditions, and partial occlusion by foliage to emulate realistic FS reception scenarios. Strong spin-photon coupling was maintained, as confirmed by persistent rabi oscillations and normal-mode splitting. An instantaneous peak output of 4.29 mW (+6.32 dBm) from a 0.01% DAP:PTP gain medium. with a pulse duration of ~4 μs, marks a performance benchmark for directly coupled masers. These findings demonstrate a proof-of-concept for masers as viable platforms for short-range, interference-resilient coherent microwave links, with future relevance to quantum sensing and secure communication technologies.
Molecular room temperature masers have emerged as promising sources of coherent microwaves, but systematic comparisons of organic gain media under uniform conditions remain limited. This paper presents a characterization of two systems, pentacene doped para terphenyl (Pc:PTP, 1.45 GHz) and 6,13 diazapentacene doped para terphenyl (DAP:PTP, 1.478 GHz), examined at four concentrations, including a new 0.05 percent DAP:PTP sample. By evaluating L band masing media under identical conditions, optimal doping levels and gain materials for high power operation are identified. The optimized system produced room temperature continuous wave masing with a peak output of 2.34 mW (+3.69 dBm), marking the first milliwatt level emission from an organic maser. Spectral coherence times of 465 ns and coherence lengths up to 150 m were obtained. Coupling to a high Q cavity mode enables collective spin photon interactions, with Rabi oscillations revealing coherent ensemble dynamics. Frequency domain analysis shows normal mode splitting of 1.37 MHz for Pc:PTP and 2.14 MHz for DAP:PTP, confirming strong coupling. Cavity QED analysis yields cooperativities C* = 304-803 for Pc:PTP and 405-1071 for DAP:PTP, among the highest for organic systems. Quantitative metrics of signal to noise ratio, spectral coherence distance, and throughput demonstrate the potential of these masers for radar, secure communication, and quantum interface technologies.
Masers can deliver ultralow-noise amplification of microwave signals in medical imaging and deep-space communication, with recent research being rekindled through the discovery of gain media operating at room-temperature, eschewing bulky cryogenics that hindered their use. This work shows the discovery of 6,13-diazapentacene doped in para-terphenyl (DAP:PTP) as a maser gain medium that can operate at room-temperature, without an external magnetic field. With a maser output power of -10 dBm, it is on par with pentacene-doped para-terphenyl in masing power, while possessing compelling advantages such as faster amplification startup times, being pumped by longer wavelength light at 620 nm and greater chemical stability from nitrogen groups. Furthermore, the maser bursts from DAP:PTP allow one to reach the strong coupling regime for cavity quantum electrodynamics, with a high cooperativity of 182. The optical and microwave spin dynamics of DAP:PTP are studied in order to evaluate its capabilities as a maser gain medium, where it features fast intersystem crossing and an advantageously higher triplet quantum yield. The results pave the way for the future discovery of similar maser materials and help designate them as promising candidates for quantum sensors, optoelectronic devices and the study of cavity quantum electrodynamic effects at room-temperature.
An increasing number of small ventures are launching missions to space with small volume satellite platforms. These small spacecraft are now being seriously considered for deep-space missions, creating a need for ground stations capable of detecting the faint signals they will transmit to Earth. Here, recent developments in room-temperature solid-state masers are reviewed to determine their readiness for use as a cheap low-noise amplifier for deep-space communications. Masers based on Pentacene-doped Para-terphenyl (Pc:PTP), Pentacene-doped Picene, Diazapentacene-doped Para-Terphenyl (DAP:PTP), Phenazine/1,2,4,5-Tetracyanobenzene (PNZ/TCNB) co-crystal, NV Diamond, Cuprous Oxide, and Silicon Carbide are considered for comparison. Pc:PTP offers good spin polarisation density and output power but suffers from thermal dissipation problems, DAP:PTP may help to obtain a lower threshold power than that achieved with Pentacene, PNZ/TCNB stands out in spin polarization density but has not achieved room-temperature masing, and NV Diamond is the only medium to have sustained continuous operation but has very limited power output. The other gain media proposed offer theoretical advantages but have not been tested in a working maser device.
Masers, the microwave analogs of lasers, have seen a renaissance owing to the discovery of gain media that mase at room temperature and zero-applied magnetic field. However, despite the ease with which the devices can be demonstrated under ambient conditions, achieving the ubiquity and portability, which lasers enjoy, has to date remained challenging. We present a maser device with a miniaturized maser cavity, gain material, and laser pump source that fits within the size of a shoebox. The gain medium used is pentacene-doped para-terphenyl, and it is shown to give a strong masing signal with a peak power of −5 dBm even within a smaller form factor. The device is also shown to mase at different frequencies within a small range of 1.5 MHz away from the resonant frequency. The portability and simplicity of the device, which weighs under 5 kg, paves the way for demonstrators particularly in the areas of low-noise amplifiers, quantum sensors, cavity quantum electrodynamics, and long-range communications.
Coherent sources exploiting the stimulated emission of non-equilibrium quantum systems, i.e. gain media, have proven indispensable for advancing fundamental research and engineering. The operating electromagnetic bands of such coherent sources have been continuously enriched for increasing demands.Nevertheless, for a single bench top coherent source, simultaneous generation of radiation in multiple bands, especially when the bands are widely separated, present formidable challenges with a single gain medium. Here, we propose a mechanism of simultaneously realizing the stimulated emission of radiation in the visible and microwave bands, i.e. lasing and masing actions, at ambient conditions by utilizing photoexcited singlet and triplet states of the pentacene molecules that are doped in p-terphenyl. The possibility is validated by the observed amplified spontaneous emission (ASE) at 645 nm with a narrow linewidth around 1 nm from the pentacene-doped p-terphenyl crystal used for masing at 1.45 GHz and consolidated by a 20 fold lower threshold of ASE compared to the reported masing threshold. The overall threshold of the pentacene-based multiband coherent source can be optimized by appropriate alignment of the pump-light polarization with the pentacene's transition dipole moment. Our work not only shows a great promise on immediate realization of multiband coherent sources but also establishes an intriguing solid-state platform for fundamental research of quantum optics in multiple frequency domains.
Through their ability to achieve cryogenic levels of noise performance while operating at room temperature, optically-pumped, solid-state (OPSS) masers show great promise as quantum sensors, oscillators, and amplifiers. We here demonstrate maser oscillation in a microwave cavity containing a crystal of pentacene-doped para-terphenyl (ptc:ptp) pumped by a single, chip-scale LED. Here, unlike previous work, the size of the pump source does not dominate the size of the maser system as a whole. This miniaturization is achieved through invasive optical pumping in the form of a waveguide, the tip of which is embedded into the maser crystal. Using experimental measurements combined with microwave and optical simulations, we find that our approach offers at least a factor-of-2 enhancement in cooperativity over end-on optical excitation. We use our simulations to define a figure of merit for maser pumping efficiency, and conclude that there remains significant headroom to improve the performance of ptc:ptp masers through improved optical design.