Piezoelectric-transducer-based optoelectronic frequency synchronizer for control of pulse delay in a femtosecond passively mode-locked Ti:sapphire laser

Abstract

We propose a piezoelectric transducer-(PZT-) based optoelectronic frequency synchronizer to control simultaneously change in the repetition rate, the relative pulse delay, and the phase noise of a passively mode-locked femtosecond Ti:sapphire laser with an intracavity saturable Bragg reflector absorber with respect to an electronic frequency reference. An optoelectronic phase-locked-loop-based PZT feedback controller with a proportional, integral, and differential (PID) circuit and a tunable voltage regulator is designed to achieve frequency synchronization, phase-noise suppression, and delay-time tuning. When the controlling voltage is tuned from -2.6 to 2.6 V, the maximum pulse-delay range, tuning slope, and tuning resolution of the laser pulse-train are 11.3 ns, 2.3 ps/mV, and 1.2 ps, respectively. Setting the gain constant of the PID circuit at 10 or larger causes the delay-time tuning function to be linearly proportional to the controlling voltage. In the delay-time tuning mode the uncorrelated single-side-band phase-noise density of the frequency-synchronized laser is approximately -120 dBc/Hz at an offset frequency of 5 kHz, which is only 7 dBc/Hz higher than that of the electrical frequency reference. The proposed system also supports linear,continuous switching,and programmable control of the delay time of Ti:sapphire laser pulses when they are frequency synchronized to external reference clocks.

Review of terahertz and subterahertz wireless communications

“…Clearly, in a realistic THz communication link, the THz transmitter and receiver cannot be synchronized by the same source. For the case of a THz link based on time-domain THz, Lin et al 103 suggest using a Piezoelectric-transducer-based optoelectronic phase lock loop to lock two separate Ti:sapphire lasers. This method could be applied to lock the repetition rates of two lasers at transmitting and receiving stations to a remotely distributed clock signal ͑for example͒ from a global positioning system.…”

Environmentally Stable 1.56-μm Femtosecond Laser System With Discontinuous Selectable Repetition Rate

“…Reference [5] achieves a pulse tuning range of about 1.1 MHz by applying optical delay lines in the linear arm of a sigma cavity, while Ref. [10] achieves pulse tuning range of kHz by applying PZTs with nanometer accuracy. Most often, pulse tuning is used for repetition rate stabilization with an accuracy in the order of millihertz or even microhertz [11].…”