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Description

Bright Polarization-Entangled Photon Source – Narrowband Telecom C‑Band

This bright polarization-entangled photon source is a high-performance, fiber-integrated platform designed to deliver abundant, low-noise entangled photon pairs in the telecom C‑band around 1550 nm. By combining a periodically poled lithium niobate (PPLN) type‑2 waveguide with a fiber-based Sagnac interferometer and a built‑in, ultra‑narrow-linewidth pump laser at 775 nm, the source achieves exceptional pair generation efficiency, high heralding efficiency, and excellent state fidelity. The system is fully engineered for turnkey, room‑temperature operation, making it an ideal entanglement source for both laboratory research and deployable quantum systems.

At the heart of the device is a periodically poled nonlinear waveguide (PPNW) that exploits strong optical confinement to significantly enhance spontaneous parametric down-conversion (SPDC). The PPLN waveguide is thermally stabilized to maintain optimal phase‑matching conditions, ensuring a consistent, narrowband output over extended operation. A fiber‑based Sagnac loop architecture provides intrinsic phase stability through self‑compensation, so users benefit from long‑term interferometric stability without the need for active alignment or frequent recalibration. This design philosophy aligns with leading entangled photon sources used in quantum communication testbeds and research laboratories worldwide, where reliability and repeatability are crucial.

The integrated pump laser is a single‑frequency external cavity source operating at 775 nm, chosen for its ultra‑narrow linewidth and excellent spectral purity. It is coupled directly into the PPLN waveguide and can be finely controlled via a built‑in variable optical attenuator. By adjusting the pump power, users can tune the photon pair generation rate, manage accidental coincidences, and optimize the signal‑to‑noise ratio for specific experiments. A rotatable half‑wave plate (HWP) further refines the distribution of pairs between the two interferometric paths, enabling precise control of the polarization reference bases and the relative weighting of different entangled components. This level of control supports demanding quantum optics protocols, including high‑dimensional encoding and advanced entanglement manipulation schemes.

To guarantee clean, application‑ready photon pairs, the source incorporates an internal optical filtering stage that removes residual pump light and suppresses associated fluorescence noise before the photons reach the output ports. The polarization-entangled pairs are routed by a polarizing beam splitter (PBS) that forms part of the Sagnac loop itself, avoiding extra insertion loss and preserving the intrinsic brightness of the source. The result is a narrow spectral bandwidth of only a few nanometers in the telecom C‑band, compatible with standard single‑mode fiber infrastructure and commonly used DWDM channel spacings. This makes the device particularly well suited for integration into existing fiber networks and for experiments requiring long‑distance quantum transmission.

In typical use, the source simultaneously provides polarization and frequency entanglement, allowing users to switch or trade off between polarization and energy‑time entanglement as needed. This dual‑domain entanglement capability is a key asset for advanced quantum communication protocols such as superdense teleportation, multi‑degree-of-freedom encoding, and hybrid continuous‑discrete variable schemes. Comparable systems used in cutting‑edge quantum key distribution, quantum repeater research, and photonic quantum computing rely on similar architectures, but this source stands out for its combination of high brightness, low noise, and all‑fiber ruggedization.

The overall package is conceived as a rugged, alignment‑free subsystem that can be directly integrated into larger quantum platforms. Its turnkey operation at room temperature, together with built‑in stabilization and noise suppression, reduces setup overheads and operational complexity. Researchers and system integrators can quickly deploy the unit in quantum key distribution trials, quantum information processing experiments, quantum LIDAR demonstrations, and other quantum sensing or communication scenarios. With its high coincidence rates, strong heralding performance, and telecom compatibility, this narrowband bright polarization-entangled photon source provides a robust foundation for state‑of‑the‑art quantum optics and quantum information applications.

Bright Polarization Entangled Photon Source

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Specifications

Operating Wavelength: 1550 nm
Wavelength Stability: -0.7 – 0.7 nm
Pump Laser Power: 0 – 12 mW
Pump Laser Wavelength: 775 nm
Signal/idler Center Wavelength: 1550 nm
Signal/idler Spectral Region: C Band
Waveguide Type: Periodically poled lithium niobate (PPLN) type-2 waveguide
Nonlinear Structure: Periodically poled nonlinear waveguide (PPNW)
Operation Temperature: Room temperature
Phase Matching Stabilization: Thermally stabilized PPNW
Pump Laser Type: Single frequency external cavity laser
Pump Laser Linewidth: Ultra-narrow (exact value not specified)
Output Photon Spectral Bandwidth: Few nanometers (narrowband)
Output Photon Characteristics: Polarization-entangled photon pairs, entangled in polarization and frequency
Interferometer Type: All-in-fiber Sagnac loop
Number Of Output Ports: 2
Output Splitting Element: Polarizing beam splitter (PBS)
Built-in Optical Components: Variable optical attenuator, rotatable half-wave plate (HWP), noise-suppression filters
Noise Filtering: Pump photons and fluorescence noise completely filtered out via built-in optical filters

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Features

  • Ultra‑Bright Entangled Photon Source – Optimized periodically poled LiNbO3 (PPLN) type‑2 waveguide in a fiber‑based Sagnac loop delivers one of the highest single and coincidence count rates available in commercial systems.
  • Narrowband C‑Band Operation (≈1550 nm) – Polarization‑entangled photon pairs generated in the telecom C‑band (centered near 1550 nm) with a narrow spectral bandwidth of only a few nanometers for low‑dispersion fiber transmission and compatibility with existing telecom components.
  • Integrated 775 nm Pump Laser – Built‑in single‑frequency external‑cavity laser at 775 nm with ultra‑narrow linewidth provides a stable, low‑noise pump without the need for additional external laser hardware.
  • High Heralding Efficiency & Fidelity – Efficient spontaneous parametric down‑conversion (SPDC) in a high‑confinement waveguide, together with low‑loss fiber coupling, yields strong heralding efficiency and excellent entanglement fidelity for demanding quantum optics experiments.
  • All‑Fiber Sagnac Architecture – Self‑compensating, alignment‑free Sagnac interferometer provides long‑term interferometric stability and phase robustness compared to bulk‑optics setups, reducing maintenance and realignment needs.
  • Built‑In Noise Suppression Filters – Internal filtering stages remove residual pump light and fluorescence background, delivering low‑noise entangled photon pairs and improving signal‑to‑noise and coincidence‑to‑accidental ratios.
  • Room‑Temperature, Turn‑Key Operation – Fully integrated design with thermal stabilization of the PPNW enables stable operation at room temperature with simple startup, ideal for both laboratory and industrial environments.
  • Thermally Stabilized Waveguide – Active temperature control of the PPLN waveguide maintains optimal phase‑matching conditions, ensuring consistent brightness, wavelength stability, and entanglement quality over time.
  • Polarization & Frequency Entanglement in One Source – Simultaneous polarization and energy‑time (frequency) entanglement supports advanced quantum communication protocols, superdense teleportation, and high‑dimensional quantum encoding.
  • Two Fiber Output Ports via PBS – Polarizing beam splitter (PBS) inside the Sagnac loop directs photon pairs into two output ports without adding excess loss, enabling straightforward integration into dual‑arm quantum communication or sensing setups.
  • Built‑In Variable Optical Attenuator – Integrated variable attenuator on the pump path allows precise control of pump power, enabling optimization of pair generation rate, accidental counts, and noise floor for different experimental regimes.
  • Rotatable Half‑Wave Plate Control – Internal rotatable HWP adjusts the relative contribution of the two interferometric paths, allowing users to tune the photon‑pair distribution between ports and switch or balance polarization vs. energy‑time entanglement bases.
  • Rugged, Alignment‑Free Design – Fiber‑integrated, compact architecture eliminates free‑space alignment, offering high mechanical stability, low sensitivity to vibration and temperature drifts, and higher uptime than bulk‑optic SPDC sources.
  • Telecom‑Compatible Fiber Interfaces – Standard single‑mode fiber outputs (typically SMF‑28 or equivalent) ensure easy coupling to existing quantum communication testbeds, deployed fiber networks, and commercial single‑photon detectors.
  • Low‑Noise, High‑Stability Long‑Term Operation – Combination of narrow‑linewidth pump, thermal control, and self‑compensating interferometer supports stable coincidence rates and entanglement visibility over extended measurement times.
  • Customizable Wavelength and Configuration – Platform can be adapted for different signal/idler wavelength combinations (within PPLN phase‑matching ranges), bandwidths, and output configurations to match specific quantum network or metrology requirements.
  • Ideal for Quantum Communication & Networking – Narrowband C‑band operation and high pair rates make this source particularly well‑suited for quantum key distribution (QKD), entanglement distribution over fiber, and quantum repeaters.
  • Ready for Quantum Computing & Information Processing – High fidelity and stability support multi‑photon interference experiments, photonic quantum computing architectures, and advanced quantum information protocols.

Applications

  • Quantum Key Distribution (QKD) – Use polarization-entangled photon pairs for secure key exchange in fiber-based and free-space QKD protocols (BBM92, E91). Ideal for long-haul telecom-band QKD over installed SMF-28 fiber infrastructure.
  • Entanglement-Based Quantum Communication Links – Deploy as a subsystem in metro and intercity quantum communication networks, quantum repeaters, and quantum relay nodes requiring narrowband C-band entangled sources.
  • Quantum Computing and Information Processing – Provide high-brightness entangled photon pairs for linear optical quantum computing (LOQC) experiments, photonic qubit gates, cluster-state generation, and scalable quantum photonics testbeds.
  • High-Dimensional Quantum Information Processing – Exploit simultaneous polarization and frequency entanglement for qudit encoding, dense information encoding, and advanced quantum state engineering schemes.
  • Superdense Coding and Teleportation – Enable polarization and frequency superdense teleportation protocols and high‑capacity quantum communication experiments that rely on high-quality entanglement fidelity.
  • Quantum Random Number Generation (QRNG) – Use correlated detection events from entangled pairs to realize high‑rate, device‑independent or semi–device‑independent QRNG systems.
  • Quantum LIDAR and Quantum Sensing – Implement quantum illumination and entanglement-assisted LIDAR schemes where correlated photon pairs enhance detection sensitivity, ranging precision, and target discrimination in noisy or low‑reflectivity environments.
  • Quantum Metrology and Precise Timing – Utilize narrowband entangled photons for phase-sensitive interferometry, dispersion measurements, clock synchronization, and time‑transfer protocols over optical fiber networks.
  • Fundamental Quantum Optics Research – Perform Bell inequality tests, entanglement swapping, quantum eraser experiments, and tests of nonlocality with a compact, stable, and room‑temperature entangled source.
  • Integrated and Fiber-Based Quantum Photonics – Seamlessly integrate into fiber‑based Sagnac interferometers, photonic integrated circuits, and lab testbeds requiring plug‑and‑play entangled sources in the telecom C‑band.
  • Quantum Networking Testbeds – Serve as a core entanglement resource for quantum network demonstrators, multi‑node entanglement distribution, and entanglement routing experiments over standard telecom fibers.
  • Education and Training in Quantum Technologies – Provide a turn‑key, alignment‑free platform for universities and R&D labs to teach quantum communication, quantum information, and entanglement-based protocols.
  • Entanglement-Based Spectroscopy and Sensing – Use frequency-correlated photon pairs for advanced spectroscopy, correlation-based measurements, and characterization of narrowband optical components in the C‑band.
  • Characterization of Single-Photon Detectors – Supply stable, high-count entangled photon pairs to calibrate and benchmark single-photon detectors, superconducting nanowire detectors, and telecom-band SPADs.
  • Subsystem for Commercial Quantum Products – Integrate as an OEM entangled photon engine in commercial QKD systems, quantum sensor platforms, and quantum-enabled test and measurement equipment.

Frequently Asked Questions

What is the OZ Optics bright polarization‑entangled photon source and how does it work?
The OZ Optics bright polarization‑entangled photon source is a turn‑key, fiber‑based quantum light source that generates pairs of polarization‑entangled photons in the telecom C‑band (around 1550 nm). It uses spontaneous parametric down‑conversion (SPDC) in a thermally stabilized, periodically poled lithium niobate (PPLN) type‑2 waveguide placed inside an all‑fiber Sagnac interferometer. A built‑in single‑frequency 775 nm external‑cavity pump laser with ultra‑narrow linewidth drives the waveguide. The Sagnac loop architecture self‑compensates many phase and polarization drifts, while integrated optical filters remove residual pump light and fluorescence noise. The result is a bright, low‑noise, narrowband entangled photon source that operates at room temperature and delivers two spatially separated output ports for quantum communication and quantum information experiments.
What are the key performance advantages of this entangled photon source compared to other commercial sources?
Compared with many bulk‑crystal and free‑space entangled photon sources, this OZ Optics source offers: (1) Very high brightness and coincidence count rates due to strong confinement in the periodically poled nonlinear waveguide and efficient fiber coupling; (2) High heralding efficiency and excellent entanglement fidelity because of the low‑loss Sagnac design and optimized type‑2 PPLN waveguide; (3) Narrowband operation in the telecom C‑band, compatible with standard DWDM and fiber‑optic infrastructure; (4) Built‑in ultra‑stable pump laser and temperature control, enabling turn‑key, alignment‑free, room‑temperature operation; (5) Integrated noise‑suppression filters that remove pump leakage and fluorescence, reducing the accidental coincidence rate; and (6) Rugged, subsystem‑ready packaging that simplifies integration into quantum key distribution systems, quantum computing testbeds, and quantum sensing platforms.
Which applications are supported by this narrowband telecom entangled photon source?
This telecom‑band entangled photon source is designed for a wide range of quantum photonics applications, including: (1) Quantum key distribution (QKD) and entanglement‑based quantum cryptography over standard optical fiber; (2) Quantum computing and quantum information processing experiments that require high‑fidelity polarization entanglement; (3) Quantum LIDAR and quantum‑enhanced sensing, where correlated photons help improve detection performance; (4) Quantum communication subsystems and testbeds, especially in the C‑band, where fiber loss is minimized; (5) High‑dimensional quantum information processing, leveraging both polarization and frequency degrees of freedom; and (6) Polarization‑ and frequency‑based superdense teleportation and related quantum networking protocols, since the source can generate photon pairs entangled simultaneously in polarization and frequency.
How are the polarization and frequency entanglement controlled or switched in this source?
The standard configuration produces photon pairs that are simultaneously entangled in polarization and frequency. Inside the fiber‑based Sagnac loop, a rotatable half‑wave plate (HWP) is integrated to control how pump light is split between the counter‑propagating paths. By adjusting the HWP, the user can control the relative amplitudes and phases of the two interferometric paths and hence the distribution of generated photon pairs between them. This allows the polarization reference bases to be defined and lets the user tune how strongly the entanglement is expressed in polarization versus the energy/frequency domain. Together with the built‑in variable optical attenuator for pump power control and external spectral filters or DWDM components, the HWP adjustment supports flexible state preparation for experiments in polarization entanglement, energy‑time entanglement, or combined hyperentangled states.
What built‑in control features does the source provide (laser, attenuation, stability, and noise suppression)?
The source is designed as a self‑contained, turn‑key quantum light module. It includes: (1) A built‑in single‑frequency external‑cavity pump laser at 775 nm with an ultra‑narrow linewidth, eliminating the need for an external pump; (2) A variable optical attenuator on the pump path that lets users finely control pump power, and thereby adjust the pair production rate and the level of accidental coincidences; (3) A thermally stabilized PPLN waveguide to maintain phase‑matching and keep the output spectrum and brightness highly stable over time; (4) An all‑fiber Sagnac interferometer that provides self‑compensation against many environmental phase and polarization fluctuations; and (5) Integrated optical filters to completely reject residual pump photons and most fluorescence noise before the entangled photons reach the output ports, improving signal‑to‑noise ratio without extra external filtering.
Is the OZ Optics entangled photon source suitable for field deployment and system integration?
Yes. The device is designed to be rugged, alignment‑free, and compatible with standard telecom fiber components, making it suitable for both laboratory and field deployments. The use of an all‑fiber Sagnac loop and a monolithic PPLN waveguide minimizes sensitivity to mechanical vibrations and temperature fluctuations. Since the pump laser, temperature control, attenuator, and filters are built in, installation is simplified to connecting power, control interfaces, and fiber output ports. This makes the source readily integrable as a subsystem in larger quantum communication networks, quantum key distribution systems, and quantum sensing platforms that require long‑term stable operation at room temperature.
What customization options are typically available for this bright entangled photon source?
The datasheet indicates the source is customizable, and comparable products on the market suggest several common customization options that are likely available on request: (1) Center wavelength and spectral bandwidth within the telecom region (e.g., specific C‑band channels or narrower linewidths for interfacing with quantum memories or DWDM systems); (2) Output connectorization and fiber types (e.g., standard single‑mode fiber, polarization‑maintaining fiber, or specific connector types); (3) Pump power range and control interfaces for laboratory or OEM integration; (4) Degree and type of entanglement (e.g., optimization for polarization, frequency, or combined hyperentangled states); and (5) Packaging form factor and environmental specifications tailored for rack‑mount, benchtop, or field‑deployable systems. For precise customization details, users should contact OZ Optics with their wavelength, bandwidth, and integration requirements.

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