Influence of lasers propagation delay on the sensitivity of atom interferometers

In atom interferometers based on two photon transitions, the delay induced by the difference of the laser beams paths makes the interferometer sensitive to the fluctuations of the frequency of the lasers. We first study, in the general case, how the laser frequency noise affects the performance of the interferometer measurement. Our calculations are compared with the measurements performed on our cold atom gravimeter based on stimulated Raman transitions. We finally extend this study to the case of cold atom gradiometers.     

Common-mode noise rejection using fringe-locking method in WEP test by simultaneous dual-species atom interferometers

We theoretically investigate the application of the fringe-locking method(FLM) in the dual-species quantum test of the weak equivalence principle(WEP).With the FLM,the measurement is performed invariably at the midfringe,and the extraction of the phase shift for atom interferometers is linearized.For the simultaneous interferometers,this linearization enables a good common-mode rejection of vibration noise,which is usually the main limit for high precision WEP tests of the dual-species kind.We note that this method also allows for an unbiased determination of the gravity accelerations difference,which meanwhile is ready to be implemented.     

High-order inertial phase shifts for time-domain atom interferometers

High-order inertial phase shifts are calculated for time-domain atom interferometers. We obtain closed-form analytic expressions for these shifts in accelerometer, gyroscope, optical clock and photon recoil measurement configurations. Our analysis includes Coriolis, centrifugal, gravitational, and gravity gradient-induced forces. We identify new shifts which arise at levels relevant to current and planned experiments. PACS 39.20.+Q; 32.80.Pj; 03.75.Dg; 04.80.-Y     

Carrier-envelope frequency stabilization of a Ti:sapphire oscillator using different pump lasers: part II

Complementing an earlier report (Vernaleken et al. in Opt Exp 20:18387, 2012), we investigate the residual phase jitter of a carrier-envelope frequency stabilized Ti:sapphire oscillator when pumped by additional commercially available pump lasers that were not part of the first study. We find that all tested pump lasers allow stabilization of the oscillator with a residual rms phase noise (integrated between 2 Hz and 5 MHz) of less than 150 mrad despite their different design and properties. Possible sources of technical noise and their elimination for specific models are discussed.     

Spectral mirror for ultra-short, high peak power, multi-PW Ti:sapphire lasers

A multilayer mirror for spectral filtering adapted to ultra-short and multi-PW Ti:Sa laser has been designed, manufactured and characterized. The method used to determine both the reflectivity shape and the coating design leads to global compensation of gain narrowing, saturation and spectral phase. The result is a spectral control on 200 nm range while keeping a flat spectral phase. This kind of filter will enable obtaining 15 fs pulse duration for multi-PW laser systems based on Ti:Sa.     

Voltage-controlled intracavity terahertz generator for self-starting Ti:sapphire lasers

A new, efficient, intracavity scheme for terahertz generation in femtosecond mode-locked Ti:sapphire lasers is proposed and demonstrated. The terahertz radiation is generated by a transient photocurrent in a GaAs layer grown on a fast semiconductor saturable absorber mirror. The average terahertz output radiation power is voltage controlled and can be electrically modulated at frequencies up to 100 kHz.     

Broadband phase-coherent optical frequency synthesis with actively linked Ti:sapphire and Cr:forsterite femtosecond lasers

We link the output spectra of a Ti:sapphire and a Cr:forsterite femtosecond laser phase coherently to form a continuous frequency comb with a wavelength coverage of 0.57-1.45 microm at power levels of 1 nW to 40 microW per frequency mode. To achieve this, the laser repetition rates and the carrier-envelope offset frequencies are phase locked to each other. The coherence time between the individual components of the two combs is 40 micros. The timing jitter between the lasers is 20 fs. The combined frequency comb is self-referenced for access to its overall offset frequency. We report the first demonstration to our knowledge of an extremely broadband and continuous, high-powered and phase-coherent frequency comb from two femtosecond lasers with different gain media.     

Experimental study on injection-locked Ti:sapphire lasers

An injection-locked Ti:sapphire laser is developed,with injection locking achieved using the Pound-DreverHall technique.By measuring the dependence of output power on the pump power with various Ti:sapphire laser parameters,we experimentally studied the influences of the ring cavity length,the focal length of the pump-laser mode-matching lens,and the output-coupler transmission on the threshold and slope efficiency.The dependence of the output power on the master laser power is also investigated.The present study provides a guideline for developing a Ti:sapphire laser with high slope efficiency and low threshold.     

亚飞秒被动同步掺钛蓝宝石激光器

通过采用一种新的被动同步方案，使两束独立掺钛蓝宝石激光通过互相位调制实现稳定同步.同步维持时间超过24h，同步精度达到0.78fs. 关键词： 互相位调制 被动同步     

用于低噪声DPL激光器的高稳定性LD驱动源的研制

根据高稳定性、低噪声半导体泵浦激光器(DPL激光器)对于激光电源的要求,研制了一台工作电流可达7A、集电流慢启动和过流保护等多重保护于一体的高稳定性LD驱动源,分析了其高稳定性电源的工作原理和影响电流稳定度的主要因素,得到了电流稳定度为2.0×10-4的高稳定性电流输出。以此激光电源作为高稳定性DPL激光器的LD驱动源,获得了3.5h内功率稳定性小于4‰的激光输出。     

Phase-locked, erbium-fiber-laser-based frequency comb in the near infrared

A phase-locked frequency comb in the near infrared is demonstrated with a mode-locked, erbium-doped, fiber laser whose output is amplified and spectrally broadened in dispersion-flattened, highly nonlinear optical fiber to span from 1100 to >2200 nm. The supercontinuum output comprises a frequency comb with a spacing set by the laser repetition rate and an offset by the carrier-envelope offset frequency, which is detected with the standard f-to-2f heterodyne technique. The comb spacing and offset frequency are phase locked to a stable rf signal with a fiber stretcher in the laser cavity and by control of the pump laser power, respectively. This infrared comb permits frequency metrology experiments in the near infrared in a compact, fiber-laser-based system.     

Dual Ti:sapphire comb lasers by a fiber laser pumping scheme and a hand-sized optical frequency reference

A dual-comb laser system containing two femtosecond Ti:sapphire (Ti:S) lasers is reported, in which the ultrashort pulses are pumped by one common fiber laser and the influences of the different pumping noise are presented both in time-domain and frequency-domain. In addition, the dimensions of dual Ti:S comb system are reduced due to the implementation of one hand-sized optical frequency reference, from which the needed space and cost for two “self-reference” optics are saved.     

Comparison of the sensitivities for atom interferometers in two different operation methods

We investigated the sensitivities of atom interferometers in the usual fringe-scanning method(FSM) versus the fringelocking method(FLM). The theoretical analysis shows that for typical noises in atom interferometers, the FSM will degrade the sensitivity while the FLM does not. The sensitivity-improvement factor of the FLM over the FSM depends on the type of noises, which is validated by numerical simulations. The detailed quantitative analysis on this fundamental issue is presented, and our analysis is readily extendable to other kinds of noises as well as other fringe shapes in addition to a cosine one.     

Phase-locked control of tiled-grating assemblies for chirped-pulse-amplified lasers using a Mach-Zehnder interferometer

Multikilojoule petawatt lasers using chirped-pulse amplification are being constructed worldwide. Several systems have adopted a tiled-grating approach to meet the size requirements for the compression gratings. Grating tiles need to be precisely phased to ensure a transform-limited focal spot when focusing high-energy laser pulses in the target plane. A computer-control test system that uses a Mach-Zehnder interferometer capable of monitoring and correcting drift in the tiled-grating assemblies within the compressor is described. The differential errors due to eight gratings, within a compressor with four grating assemblies, were compensated by adjusting a single grating.     

High-power Ti:sapphire lasers for spectroscopy of antiprotonic atoms and radioactive ions

The ASACUSA collaboration has developed injection-seeded Ti:sapphire lasers of linewidth Γ_pl ～ 6 MHz, pulse energy 50–100 mJ, and output wavelength λ?=?726–941?nm. They are being used in two-photon spectroscopy experiments of antiprotonic helium atoms at the Antiproton Decelerator (AD) of CERN. Ti:sapphire lasers of larger linewidth Γ_pl ～ 100 MHz but more robust design will also be used in collinear resonance ionization spectroscopy (CRIS) experiments of neutron-deficient francium ions at the ISOLDE facility.     

Intracavity LiNbO(3) Fabry-Perot etalon for frequency stabilization and tuning of a single-mode quasi-continuous-wave titanium:sapphire ring laser

We describe an intracavity LiNbO(3) Fabry-Perot etalon for frequency stabilization and tuning of a single-mode quasi-continuous-wave Ti:Al(2)O (3) ring laser. Taking into account the 150-micros pulse duration and the 40-Hz repetition rate of our laser, we achieve stabilization by 266-kHz modulation of 100-V peak-to-peak voltage applied to the electro-optic crystal. Tuning is ensured by the presence of a gain loop that contains a lock-in amplifier reacting with a multimorphous ceramic by means of 0-300-V dc voltage, which causes slight rotation of the LiNbO(3) Fabry-Perot etalon. A continuous frequency scan of 6 GHz was made that potentially can be extended to 6 cm(-1) .     

High-resolution frequency estimation technique for recovering phase distribution in interferometers

An integral approach to phase measurement is presented. First, the use of a high-resolution technique for the pixelwise detection of phase steps is proposed. Next, the robustness of the algorithm that is developed is improved by incorporation of a denoising procedure during spectral estimation. The pixelwise knowledge of phase steps is then applied to the Vandermonde system of equations for retrieval of phase values at each pixel point. Conceptually, our proposal involves the design of an annihilating filter that has zeros at the frequencies associated with the polynomial that describes the fringe intensity. The parametric estimation of this annihilating filter yields the desired spectral information embedded in the signal, which in our case represents the phase steps. The proposed method offers the advantage of extracting the interference phase of nonsinusoidal waveforms in the presence of miscalibration error of the piezoelectric transducer. In addition, in contrast to previously reported methods, this method does not require the application of selective phase steps between data frames for nonsinusoidal waveforms.     

Comparison of three-and four-mirror resonator designs of Ti:sapphire lasers

Ti:sapphire lasers are widely used in many applications in optics; the designs of three-and four-mirror resonators are the basic configurations for these systems. In this work, we analyze the advantages and disadvantages of each configuration. The aim is to construct a simple and small tunable CW laser that can be used in laser spectroscopy. Brewster-cut laser rods and asymmetrically folded arms are modeled. With the model, the stability conditions are theoretically established as well as the compensation of astigmatism for both the pump and the signal beams. As experimental results, we characterize both configurations and discuss the main differences.     

A comparative study of approaches for spectral control of Ti:sapphire pulsed lasers

The results of a comparative study (theoretical and experimental) of two original approaches for spectral control of two-wavelength pulsed Ti:sapphire (Ti:S) lasers and the most popular conventional methods are presented. Single line operation as a particular case is considered. We compare our own methods: (i) combined dual pulse pumping–passive self-injection locking (DPP–PSIL) and (ii) coupled cavity dye laser injection locking (CCLIL) with the conventional methods: (i) intracavity selection (IS), (ii) PSIL and (iii) traditional injection locking using an external dye laser. The most important criteria—laser efficiency, emission line width, tuning range, spectral purity and buildup time are compared under optimized conditions. The comparison is made using the same pump source with constant output energy in each case. The results serve as a basis for choosing correctly the most suitable spectral control technique for a particular Ti:S laser application. It is shown that the DPP–PSIL method guarantees a remarkable improvement of the Ti:S laser performance (nearly doubling the laser efficiency with the same line width and comparable laser tuning range as IS, combined with a protection of the selectors). The CCLIL approach assures a maximum laser efficiency in narrow line emission in addition to a minimal and reproducible buildup time. The IS method provides a maximal tuning range.