Acetylene-stabilized Laser Research Articles

Iodine-stabilized laser at telecom wavelength using dual-pitch periodically poled lithium niobate waveguide.

We demonstrate the third harmonic generation of a 1542-nm laser using a dual-pitch periodically poled lithium niobate waveguide with a conversion efficiency of 66%/W2. The generated 514-nm light is used for saturation spectroscopy of molecular iodine and laser frequency stabilization. The achieved laser frequency stability is 1.1×10-12 at an average time of 1 s, which is approximately one order of magnitude better than the acetylene-stabilized laser at 1542 nm. Uncertainty evaluation and absolute frequency measurement are also performed. The developed frequency-stabilized laser can be used as a reliable frequency reference at the telecom wavelength for various applications including optical frequency combs and precision interferometric measurement.

Enhancement of the performance of a fiber-based frequency comb by referencing to an acetylene-stabilized fiber laser.

We demonstrate a significant improvement in the performance of a fiber-based frequency comb when a GPS-disciplined Rb clock is replaced with an acetylene-stabilized laser as the frequency reference. We have developed a compact, maintenance-free acetylene-stabilized fiber laser with a sub-kHz short-term linewidth and an Allan deviation below 3×10-13 for integration times above 1 s. Switching the comb reference from the Rb clock to the acetylene-stabilized laser improves both comb tooth linewidth and Allan deviation by about two orders of magnitude. Furthermore, long-term measurements of the acetylene-stabilized laser frequency with reference to the GPS-disciplined clock indicate a potential relative frequency uncertainty of 2 × 10-12.

All-optically stabilized frequency comb

We present an all-optically stabilized, erbium-doped mode-locked fiber laser with an optically pumped ytterbium-doped fiber. The mode-locked fiber laser has two frequency-control actuators that are pump laser powers for erbium-doped and ytterbium-doped fibers. We investigate the frequency-control characteristics of the mode-locked laser and find that the fixed points for the two actuators are sufficiently apart from each other, realizing the simultaneous phase locking of the repetition and carrier envelope offset frequencies. We describe a long-term frequency measurement of an acetylene-stabilized laser at 1542 nm using an all-optically stabilized frequency comb.

Optical frequency comb comparison between optical clock mode and optical frequency synthesizer mode

We report on an accuracy limit test result of the optical frequency comb technique by comparing the frequencies of two optical frequency combs that operate in two different modes. These two modes are distinguished by the reference frequency for the comb frequency stabilization; an optical frequency (in an optical clock mode) or a microwave frequency (in an optical frequency synthesizer mode). The comparison of the two combs was carried out by simultaneously measuring an absolute frequency of an acetylene-stabilized diode laser with both combs. The frequencies of the two combs agreed with each other within the uncertainty of 16 Hz at 194 THz. The uncertainty is reduced by more than an order compared with a previous report.

Widely Tunable External Cavity Laser Diode Injection Locked to an Optical Frequency Comb

We report an ultrastable external cavity laser diode (ECLD) that can be selectively injection locked to an optical frequency comb (OFC) generated by acetylene stabilized laser (ASL) seeding. The carrier envelope offset (position) and repetition rate (mode spacing) of the OFC, which functions as the master oscillator, was stabilized to the ASL (1.1 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-12</sup> at 1 s) and H-maser (2 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-13</sup> at 1 s), respectively. The ECLD can be tuned over 70 nm in the 1.5-μm region and can be discretely locked to the comb modes with 25-GHz spacing over a 10-THz span. The frequency stability of the ECLD injection locked to the OFC reached as high as 1.1 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-12</sup> for 1-s averaging time.

Visible-to-near infrared standard source generation using acetylene ( 13C 2H 2)-stabilized comb-injection-locked technique

An ultra-stable visible laser source (VLS) was generated by the second harmonic of a selectively injection-locked distributed feedback (DFB) laser from an optical frequency comb with acetylene-stabilized laser seeding. For the second-harmonic generation (SHG) of the injection-locked DFB laser, we used periodically poled lithium niobate (PPLN) crystal and generated the VLS at a region of 771 nm, which was discretely locked to a spacing of 25 GHz within the PPLN bandwidth (180 GHz). The frequency stability of this source was estimated to be 1.1 × 10 − 12 with an average time of 1 s.

Demonstration of an optical frequency synthesizer with zero carrier-envelope-offset frequency stabilized by the direct locking method

We developed an optical frequency synthesizer (OFS) with the carrier-envelope-offset frequency locked to 0 Hz achieved using the "direct locking method." This method differs from a conventional phaselock method in that the interference signal from a self-referencing f-2f interferometer is directly fed back to the carrier-envelope-phase control of a femtosecond laser in the time domain. A comparison of the optical frequency of the new OFS to that of a conventional OFS stabilized by a phase-lock method showed that the frequency comb of the new OFS was not different to that of the conventional OFS within an uncertainty of 5.68x10(-16). As a practical application of this OFS, we measured the absolute frequency of an acetylene-stabilized diode laser serving as an optical frequency standard in optical communications.

Fiber-Based Acetylene-Stabilized Laser

We describe a fiber-based acetylene-stabilized laser system in which light is coupled to free space only to pass through the acetylene cell. The system is constructed using standard components used in telecommunication networks, making the approach straightforward to implement. The Doppler-free spectrum of acetylene can be detected, even without a lock-in amplifier using simple collinear pump-probe geometry, when the length of the optical path in the spectroscopy arrangement is dithered to cancel interference that is inevitably present in a fiber-based setup. The laser was stabilized to five different transitions of 13 C2H2 at the (nu1 + nu3) band using the third-harmonic technique, and the absolute frequencies were measured with an optical frequency comb generator. All the results are in good agreement with the values recommended by the International Committee for Weights and Measures (CIPM). The method for canceling the interference presented here can conceivably be generalized to other types of stabilized lasers as well.

Absolute-Frequency Measurement of an Acetylene-Stabilized Laser Locked to the P(16) Transition of $^{13}\hbox{C}_{2}\hbox{H}_{2}$ Using an Optical-Frequency Comb

In order to establish the national frequency standards for the Korea Research Institute of Standards and Science in the 1.5-mum region, we have developed an acetylene-stabilized laser diode locked to the P(16) transition of 13C2H2. We then measured its absolute frequency using an optical-frequency comb based on a mode-locked Ti:sapphire laser whose repetition frequency and carrier-envelope offset frequency were phase locked to an H-maser. The measured absolute frequency of the laser diode locked to the P(16) transition of 13C2H2 was 194 369 569 386.0 kHz, with an uncertainty of 0.3 kHz, based on the measurements of a single system. Including the contribution of the residual offset, the uncertainty was 1.9 kHz

Practical optical frequency measurement system around 1.5 μm based on an acetylene-stabilized laser-locked optical frequency comb

We have developed a practical and precise frequency measurement system at 1.5μm telecommunication band. An electro-optic-modulator based optical frequency comb is phase-locked to a dither-free acetylene-stabilized laser to realize an optical frequency comb with frequency uncertainty of 10kHz (5×10−11) and the linewidth of 15kHz. The present frequency comb can be also used as an optical frequency reference grid defined by ITU-T (International Telecommunication Union, Telecommunication Standardization Sector). Using the present frequency measurement system, we have demonstrated the first optical frequency measurement of 12C16O overtone absorption lines around 1.56μm with the uncertainty of lower than 900kHz.

Long-term measurement of optical frequencies using a simple, robust and low-noise fiber based frequency comb

We have developed a fiber-based frequency comb system consisting of a simple mode-locked fiber laser and a backward pumping amplifier combined with a highly nonlinear fiber with a short zerodispersion wavelength. As a result, the signal to noise ratio of the obtained carrier-envelope-offset frequency beat is larger than 45 dB at a bandwidth of 100 kHz. Furthermore, we have succeeded in measuring the optical frequencies of a 1542-nm acetylene-stabilized laser and a 532-nm iodinestabilized Nd:YAG laser continuously for more than one week using the fiber-based comb system. The long-term measurement revealed that the frequency stability of the iodine-stabilized laser was 5.7 x 10(-15) with 100 000 s averaging.

Modulation-free acetylene-stabilized lasers at 1542 nm using modulation transfer spectroscopy

We report frequency stabilization of diode lasers using modulation transfer spectroscopy of an acetylene transition (13C2H2, ν1+ν3, P(16)) at 1542 nm. We realize modulation-free acetylene-stabilized lasers with a frequency stability of about 10−11 and an absolute frequency accuracy of about 20 kHz.

Frequency measurement of acetylene-stabilized lasers using a femtosecond optical comb without carrier-envelope offset frequency control

We have established a frequency measurement system for frequency-stabilized lasers operating in telecommunication wavelength bands, by using a femtosecond optical comb without the need for carrier envelope offset frequency control. This system has been used to measure the frequency of an acetylene-stabilized laser operating at 1542 nm for a period of over 10 hours. The frequency stability of the acetylene-stabilized laser is estimated to be 3x10-12 for a 10-s averaging time, improving toward 1x10-13 after 10000 s. We have measured three acetylene-stabilized lasers, including one commercially available laser, and confirmed that the frequency values are in good agreement (a frequency scatter of 2.1 kHz) with previously measured results reported by different institutes. In addition to the P(16) line of acetylene at 1542 nm, we measured the absolute frequencies of the P(24) line at 1547 nm, the P(1) line at 1534 nm, and the R(5) line at 1530 nm with a view to improving the accuracy of the acetylene frequency atlas. The acetylene-stabilized laser serves as an important optical frequency standard for telecommunication applications.

Absolute frequency measurement of an acetylene-stabilized laser at 1542 nm.

The absolute frequency of an acetylene-stabilized laser at 1542 nm is measured at its second harmonic (771 nm) by use of a femtosecond optical comb based on a mode-locked Ti:sapphire laser. Frequency stability and reproducibility of the acetylene-stabilized laser are evaluated by the femtosecond comb with a H maser as a frequency reference. The absolute frequency of a laser diode stabilized on the P(16) transition of 13C2H2 is determined to be 194 369 569 383.6(1.3) kHz. The acetylene-stabilized laser serves as an important optical frequency standard for telecommunication applications.

Accurate Optical Frequency Standards in the Optical Fiber Communication Band

We have developed accurate optical frequency standards based on acetylene absorption lines in the 1.5 μm optical fiber communication band. We realized acetylene-stabilized diode lasers with a frequency reproducibility of 10 kHz (5×10-11). We have determined the absolute optical frequency of acetylene transitions with an uncertainty of 12 kHz (6×10-11). As a result, the acetylene transition (13C2H2 P(16)) was adopted as a recommended radiation for the realization of the meter. Thus the acetylene optical frequency standard can be used as a calibration frequency reference for the wavelength-division-multiplexed (WDM) optical communication systems in the 1.5 μm region.