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.

Femtosecond-laser-based optical clockwork with instability

Two octave-spanning optical-frequency combs (750-MHz comb spacing) are phase locked to a common continuous-wave laser diode. The measured instability of the heterodyne beat between the two combs demonstrates that the intrinsic fractional frequency noise of a comb is

First international comparison of femtosecond laser combs at the International Bureau of Weights and Measures.

The first international comparison of femtosecond laser combs has been carried out at the International Bureau of Weights and Measures (BIPM). Three comb systems were involved: BIPM-C1 and BIPM-C2 from the BIPM and ECNU-C1 from the East China Normal University (ECNU). The agreement among the three combs was found to be on the subhertz level in the vicinity of 563 THz. A frequency difference measurement scheme was demonstrated that is suitable for general comb comparisons.

Optical frequency synthesis and comparison with uncertainty at the 10(-19) level.

A femtosecond laser-based optical frequency synthesizer is referenced to an optical standard, and we use it to demonstrate the generation and control of the frequency of electromagnetic fields over 100 terahertz of bandwidth with fractional uncertainties approaching 1 part in 10(19). The reproducibility of this performance is verified by comparison of different types of femtosecond laser-based frequency synthesizers from three laboratories.

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.

Comparison of 127I2-stabilized frequency-doubled Nd:YAG lasers at the Bureau International des Poids et Mesures.

A frequency comparison was carried out between iodine-stabilized Nd:YAG lasers at 532 nm from the Bureau International des Poids et Mesures, the Centre for Metrology and Accreditation, the Czech Metrology Institute, and the Bureau National de Métrologie-Institut National de Métrologie. The frequency differences between lasers, as well as the frequency reproducibility of each system,were investigated. Pressure-, modulation-, and power-induced shifts were studied. A frequency dispersion (1 sigma) of 3.5 kHz (6.2 x 10(-12) in relative terms) with an average reproducibility for each laser of the order of 0.4 kHz (7.1 x 10(-13) in relative terms) was observed over the duration of the comparison. Relative stabilities better than 1 x 10(13) at 1 s were demonstrated for the third-harmonic systems.