Power enhancement of burst-mode ultraviolet pulses using a doubly resonant optical cavity.

We report a doubly resonant enhancement cavity (DREC) that can realize a simultaneous enhancement of two incoming laser beams at different wavelengths and different temporal structures. The double-resonance condition is theoretically analyzed, and different DREC locking methods are experimentally investigated. Simultaneous locking of a Fabry-Perot cavity to both an infrared (1064 nm) and its frequency-tripled ultraviolet (355 nm) pulses has been demonstrated by controlling the frequency difference between the two beams with a fiber-optic frequency shifter. The DREC technique enables novel applications of optical cavities to power enhancement of burst-mode lasers with arbitrary macropulse width and repetition rate.

Spherical reference cavities for frequency stabilization of lasers in non-laboratory environments.

We present an optical cavity design that is insensitive to both vibrations and orientation. The design is based on a spherical cavity spacer that is held rigidly at two points on a diameter of the sphere. Coupling of the support forces to the cavity length is reduced by holding the sphere at a "squeeze insensitive angle" with respect to the optical axis. Finite element analysis is used to calculate the acceleration sensitivity of the spherical cavity for the ideal geometry as well as for several varieties of fabrication errors. The measured acceleration sensitivity for an initial, sub-ideal version of the mounted cavity is 4.0(5)×10(-11)/g, 1.6(3)×10(-10)/g, and 3.1(1)×10(-10)/g (where g = 9.81 m/s2) for accelerations along the vertical and two horizontal directions, and the fractional frequency stability of a laser locked to the cavity is 1.2×10(-15) between 0.4 and 13 s. This low acceleration sensitivity combined with the orientation insensitivity that comes with a rigid mount indicates that this cavity design could allow frequency stable lasers to operate in non-laboratory environments.

Systematic study of the 87Srclock transition in an optical lattice.

With ultracold 87Srconfined in a magic wavelength optical lattice, we present the most precise study (2.8 Hz statistical uncertainty) to date of the 1S0-3P0 optical clock transition with a detailed analysis of systematic shifts (19 Hz uncertainty) in the absolute frequency measurement of 429 228 004 229 869 Hz. The high resolution permits an investigation of the optical lattice motional sideband structure. The local oscillator for this optical atomic clock is a stable diode laser with its hertz-level linewidth characterized by an octave-spanning femtosecond frequency comb.

Simple and compact 1-Hz laser system via an improved mounting configuration of a reference cavity.

We report an improved mounting configuration for a passive optical cavity used for laser frequency stabilization. The associated reduction of the vibration sensitivity of the effective cavity length has led to a simple and compact reference cavity system for laser stabilization at the level of 1 Hz linewidth.

Ultralow-jitter, 1550-nm mode-locked semiconductor laser synchronized to a visible optical frequency standard.

Using high-bandwidth feedback, we have synchronized the pulse train from a mode-locked semiconductor laser to an external optical atomic clock signal and achieved what is to our knowledge the lowest timing jitter to date (22 fs, integrated from 1 Hz to 100 MHz) for such devices. The performance is limited by the intrinsic noise of the phase detector used for timing-jitter measurement. We expect such a highly stable device to play an important role in fiber-network-based precise time/frequency distribution.

Subfemtosecond timing jitter between two independent, actively synchronized, mode-locked lasers.

With the implementation of a fast-bandwidth servo, along with improved laser construction and associated better passive stability, we have achieved subfemtosecond relative timing jitter between two independent, actively synchronized, mode-locked Ti:sapphire lasers. Timing jitter of 0.58 fs is obtained with a 160-Hz observation bandwidth over several seconds. Within a 2-MHz observation bandwidth, the timing jitter is 1.75 fs. Excellent repeatability and rapid speed in setting an arbitrary time delay between two pulses are also demonstrated.