Temporal Shaping and Measurement of Pulsed Quantum Light

Single photon manipulation and measurement is a critical necessity to quantum information processing and communication. Developing techniques for shaping the flying single-photon states is a crucial task in quantum technology as they should be coherent operations that preserve the quantum state of the photons.In this thesis, the time-frequency degree of freedom is considered for information encoding as it offers a high dimensional information encoding platform. To realize the spectral-temporal pulse shaping, nonlinear optical methods are most often used in optical signal processing but they are not applicable in low light regime. In this thesis, an electro-optic approach is taken to manipulate the single photon in the time-frequency domain which is electro-optic phase modulation. This approach is a coherent and deterministic operation that can be applied to both classical and quantum light pulses. The first task within the thesis was to characterize the temporal phase modulation process in which a time-varying phase is applied to the optical pulses. In such a scheme, the electro-optic phase modulator is driven by the time varying electronic signal taken from a fast photodiode that is amplified and then synchronized with the optical pulse passing through the modulator. This characterization was performed using the electro=optic sampling technique. In the second task, a method for measuring single photon pulse envelope is presented. An interferometric optical setup was developed where the optical pulse is employed to measure itself. The optical pulse propagates through a balanced Mach-Zehnder interferometer where a tunable spectral shear is applied to one arm of the interferometer. The frequency of the optical pulse is scanned with respect to its replica in the reference arm. Then a photodiode at the output of the interferometer is used to measure the integrated energy per pulse as a function of the spectral shear. This measurement yields an interference fringe pattern in the spectral domain. One can take the Fourier transform of the interference fringes to obtain the energy envelope of the optical pulse in the time domain. This technique was employed to measure the energy envelope of both classical and quantum light pulses. This novel technique can measure temporal duration of short optical pulses without time-resolved and spectrally-resolved detection and is central wavelength independent and intrinsically free of photon noise. In the third task, optical devices based on grating structures were fabricated and characterized for passive shaping optical pulses. One promising platform to realize such a device is chirped fiber Bragg grating (CFBG) structures. The CFBGs can be engineered to deliver arbitrary dispersion and spectral profiles. In the CFBG structures, a specific apodization (amplitude) grating profile can be applied through the grating fabrication process, in a way to achieve desired spectral reflectivity response. The group velocity dispersion can also be controlled through engineering the positioning of Bragg gratings inside the optical fiber. In this task, chirped grating samples at telecom and two micron wavelengths with specific dispersion, reflectivity and bandwidth were fabricated. In summary, I worked on advancing the use of electro-optic approach for manipulation of short optical pulses that is applicable in both classical and quantum regimes. The presented approach gives an active control for shaping of optical pulses. Based on this electro-optic approach, the tunable spectral shearing interferometry technique for measuring single photon pulse was introduced. In addition, the chirped Bragg grating structures for passive shaping of optical pulses was fabricated. These sets of developed optical devices open new ways in optical pulse shaping for quantum information processing and communication.