Widely tunable single photon source with high purity at telecom wavelength.

Area of Science:

• Quantum Optics
• Nonlinear Optics
• Solid-State Physics

Background:

• Spontaneous parametric down-conversion (SPDC) is a key process for generating quantum light sources.
• Achieving high spectral purity and tunability is crucial for practical quantum information and communication systems.
• Periodically poled crystals, like KTiOPO(4) (PPKTP), offer engineered nonlinearities for efficient photon generation.

Purpose of the Study:

• To investigate the spectral tunability and purity of photon pairs from SPDC in a PPKTP crystal.
• To explore the performance of the photon source under group-velocity matching conditions.
• To assess the suitability of this source for telecommunication wavelength applications.

Main Methods:

• Theoretical investigation using numerical simulations of SPDC.
• Experimental generation and characterization of photon pairs using a PPKTP crystal.
• Measurement of joint spectral intensity and calculation of Schmidt numbers to quantify spectral purity.

Main Results:

• Numerical simulations predict spectral purity > 0.81 for wavelengths from 1460 nm to 1675 nm (S-, C-, L-, and U-bands).
• Experimental measurements at 1565 nm, 1584 nm, and 1565 nm yielded high Schmidt numbers (1.01, 1.02, 1.04), indicating excellent spectral purity.
• The generated photon pairs are spectrally tunable across a wide range of telecommunication wavelengths.

Conclusions:

• The developed photon source exhibits excellent spectral purity and tunability, meeting the requirements for quantum information and communication.
• Group-velocity matching in PPKTP crystals is an effective strategy for optimizing SPDC sources.
• This research provides a promising platform for advancing quantum technologies operating at telecommunication frequencies.