Main Specification

780 nm single frequency laser

Continuous, high power, low drift, narrow linewidth, tunable, linear polarization, stable environment

The 780 nm single-frequency laser, which is resonated with Rb atom 5²S_1/2-5²P_3/2 energy level transition, can be used for laser cooling, quantum regulation and detection of Rb atom. Therefore, it is essential in the Rb atom based atomic clocks, atomic magnetometers, atomic interferometers, atomic gravimeters, atomic gyroscopes and atomic gravity gradiometers. It is also indispensable in the Rb atom-based quantum simulation, atomic and molecular spectroscopy, BEC and other scientific research applications.
In these applications, higher laser power will lead to more cold atoms, a larger interaction area between light and atoms, and a more uniform force; Lower drift of the laser can ensure longer and more stable Doppler-free frequency stabilization with Rb atoms. Narrower linewidth of the laser can reduce the noise of atomic detection and obtain higher SNR. The stability against the environment makes the laser insensitive to ambient temperature and vibration, Therefore, there are significance in the application of atomic clocks, magnetometers, and atomic interferometers-based gravimeters/gyroscopes/gravity gradiometers. It is necessary for portable instruments.

780 nm single frequency laser scheme
 

PreciLasers develops the 780 nm fiber laser which includes a 1560 nm seed laser, an Er-doped fiber amplifier and a periodically poled crystal. The all-solid-state laser contains no manually adjustable mechanical parts. It insensitive to vibration and temperature, and in possession of excellent environmental stability. Due to utilizing EFA as an amplifier, the output power of 780 nm laser can be up to 15 W.
Seed Laser

The frequency drift, linewidth and tuning characteristics of the 780 nm laser developed by PreciLasers depend on the 1560 nm seed laser. Two types of seed lasers are adopted in the frequency doubling scheme. One is the fiber DFB laser, the other is the external cavity diode laser.

The characters of two 1560 nm seed lasers
 

The DFB seed laser of PreciLasers                                               The ECDL seed laser of PreciLasers

 Both seed lasers can provide a narrow linewidth low drift tunable 1560 nm laser. The fiber DFB laser takes the gain fiber DFB grating as both the resonant cavity, the gain medium and the mode selection element so no mode hopping tunning(1nm) and narrow linewidth(<10kHz) can be achieved in full range. Using PZT as fast tuning element, tuning bandwidth and range can be 5kHz and 3GHz respectively. The ECDL seed laser uses volume grating as the mode selection element and has a resonant cavity with integrated fixed structure. The mode-free temperature tuning range of The ECDL seed laser is 7 GHz through tuning the temperature and the current. Because utilizing the current tuning, the fast-tuning bandwidth can reach 1 MHz, and the corresponding tuning range is 500 MHz.
Both kinds of seed laser are in all-solid-state structure, and have high vibration resistance and temperature stability. The vibration resistance of ECDL can even reach the aerospace class. Due to the excellent environmental stability, both seed lasers have the characteristics of low drift, which is less than 200 MHz at room temperature.

0.97 kHz linewidth measured by time-delay self-heterodyne beat
 

The center frequency drift of the seed laser at <25 MHz@8hrs

Er-doped Laser Amplifer(EFA）

When EFA developed by PreciLasers amplifies the seed laser power, the increase of the frequency and intensity noise is kept in extreme low range. The linewidth is less than 10 Hz, and the intensity noise (RIN) is less than -140 dBc/ HZ@ 100 kHz. Compared to the scheme of directly power-amplified 780 nm diode laser, the scheme of utilizing Er-doped fiber amplifier (EFA) as 1560 nm laser amplifier adopted by PreciLasers can get higher power. The maximum laser power outputted with stable and long lifetime by EFA can be up to 15 W. Due to all fiber structure, the EFA have excellent environmental stability.

Low noise single frequency 1560nm fiber amplifier

Space output 780 nm single frequency laser FL-SF-780

To meet the demands of the atomic physics and quantum physics based on Rb atom, PreciLasers has developed space output 780 nm laser with maximum power of 15W using frequency doubling technique. Due to Handling, low drift, anti-vibration and other excellent environmental adaptability, FL-SF-780nm has been used in out laboratory experiments of Rb atom interferometer and has been frequency stabilized with saturated absorption spectrum for several months.

• Narrow linewidth<20 kHz (as low as 2 kHz)
• Optional low intensity noise (RIN <-130 dBc/Hz @ 100 kHz)
• High power(15W)
• Excellent beam quality (M² <1.1)
• Power stability (P-P<1% @25℃, <2% @15-35℃)
• Environmental stability (15-35℃, 0.5 Grms (0-200 Hz))
• Rb atom
• Magic light lattice

1 Can be Costumed；Custom range765-795 nm
2 Depending on the seed laser, the seed laser can be external
3 Low noise seed can be selected for low noise

Fiber output 780 nm single frequency laser FL-SF-780

To meet the demands of the atomic physics and quantum physics based on Rb atom, PreciLasers has developed fiber output 780 nm laser with maximum power of 2W using waveguide frequency doubling technique. Due to Handling, low drift, anti-vibration and other excellent environmental adaptability, FL-SF-780nm has been used in out laboratory experiments of Rb atom interferometer and has been frequency stabilized with saturated absorption spectrum for several months.

• Narrow linewidth<20 kHz (as low as 2 kHz)
• Optional low intensity noise (RIN <-130 dBc/Hz @ 100 kHz)
• High power(2W)
• Excellent beam quality (M² <1.1)
• Power stability (P-P<1% @25℃, <2% @15-35℃)
• Environmental stability (15-35℃, 0.5 Grms (0-200 Hz))
• Rb atom

1 Can be Costumed；Custom range 765-795 nm
2 Depending on the seed laser, the seed laser can be external
3 Low noise seed can be selected for low noise

780 nm single frequency laser FL-SF-780

Dual fiber output single frequency laser at 780 nm, FL-SF-780-2

PreciLasers develops the dual-channels single frequency fiber laser with the maximum output power up to 1W/2W for Gravimeter gradiometer based on Rb cold atom. The frequency difference between the two channels can be locked by beat frequency/phase locking technique. The output ports of 1560/780 nm laser can be ordered, which provides high performance light source for gravimeter, quantum optics and so on. The seed laser, amplifier and frequency doubling module of dual-channel 1560 nm laser are integrated in a small air-cooling case. The whole machine has compact structure, stable and reliable performance, and can pass vibration and high-low temperature tests.

• Narrow linewidth<20 kHz (as low as 2 kHz)
• Optional low intensity noise (RIN <-130 dBc/Hz @ 100 kHz)
• High power(2W)
• Excellent beam quality (M² <1.1)
• Power stability (P-P<1% @25℃, <2% @15-35℃)
• Environmental stability (15-35℃, 0.5 Grms (0-200 Hz))
• Rb atom
• Magic light lattice
• Optical tweezer

■High and low temperature impact performance
■ Frequency stability under high and low temperature impact
■High low temperature storage

Center frequency drift of 0℃-50℃ is about 340 MHz, and the center frequency drift of 25℃ for 2 hours is about 40 MHz
The experiment of high and low temperature impact storage at -30℃-70℃ showed that the laser normal operation after high and low temperature shock.

■RMS power stability under high and low temperature impact

 

When the ambient temperature changes from 0℃-50℃ at interval of 10 ℃. Although the laser power will jump during the temperature change process the power will remain stable at each temperature.

The stability of the first channel at each temperature point in the high-low temperature test was measured. The power stability of the 2-hour RMS at the limiting temperature of 0℃ and 50℃ was better than 0.2%
The power stability of the second channel is also better than 0.2% (single temperature point, RMS)

■Frequency tuning test

The seed has a reserved frequency sweep interface, and the 780nm laser frequency sweep range is about 3.2GHz.  

EFA-SSHG-780-2 size

Selecting a reasonable frequency locking point and controlling an appropriate frequency difference and frequency shift between the two channels, a dual-channels 780 nm laser produced by PreciLasers can provide all the lasers required for the experiment of rubidium atomic gravimeter. The product has good environmental adaptability and is an excellent choice for laser source of transportable atomic gravimeter.

 780nm laser frequency locking module

Cold atom experiments with Rb need lasers with specific frequency and PreciLasers launches different frequency locking schedules for 780nm laser. We built up an all-fiber-connected frequency locking module with an integrated optical system and other optical fiber devices. This module can offer stable SAS or MTS signal and together with our laser controller Preci-Lock, frequency locking with good long-term stability is realized.
The frequency difference between two lasers should keep to a constant value in some cold atom experiments. For 87Rb atom gravimeter, the frequency difference of cooling laser and repumping laser should be about 6.6GHz and for the two Raman lasers the value is 6.834GHz. PreciLasers has launched a specialized laser controller Preci-Beat for offset frequency locking in the range from 50MHz to 8GHz with beat frequency/phase locking technique.
◆Integrated optical module
With integrated spatial frequency-locking module, PreciLasers builds an all-fiber-connected frequency locking module. This module gives a stable SAS or MTS signal at Rb D2 line and the spectrum can offer error signal for frequency locking of 780nm laser.

◆Multi-function laser controller

PreciLasers offers a multi-function laser controller for frequency locking under different condition. The controller, which is named Preci-Lock，is integrated with modem, PID module and High-Voltage amplifier and it can work as error signal generator, PID servo and PZT driver at the same time. All function of Preci-Lock is controlled by software with no physical button or knob. The controller can work in different mode under customized. Under internal-modulation mode laser is locked with SAS or AS while under external-modulation mode laser is locked with MTS or PDH technique.

For multi-channel lasers, Preci-Lasers offers another laser controller Preci-Beat for offset frequency locking. Preci-Beat is integrated with PFD and PID module and is also controlled with software.
 

◆SAS-locking
Frequency locking with SAS is based on Lock-in amplifier. Take the SAS of 85Rb atom as example, Preci-Lock get SAS signal from integrated optical module and generate error signal with lock-in amplifier, the PID module in Preci-Lock will then lock the frequency of 780nm laser.

 

SAS and error signal in Preci-Lock software

We build two independent SAS-locking system for 780nm laser and take a laser beating test with their 1560nm seed laser. This can show the stability of frequency locking.

• Locking precision：<±100kHz（23h）
• Frequency stability：<1×10-11（1000s）

◆MTS-locking
Unlike SAS-locking, MTS-Locking is under extern-modulation mode and the spectrum signal getting from demodulation can directly serve as error signal. Also take the MTS of 85Rb atom as example, integrated optical module provide both SAS signal and modulated MTS signal to Preci-Lock. After demodulation, the MTS signal will be error signal for frequency locking while the SAS signal here will be a reference signal. Due to their different principles, locking point of MTS and SAS are not the same.

SAS (reference) signal and MTS (error) signal in Preci-Lock sofeware

 

Take also the beating test with two independent MTS-locking module.

Locking precision：<±100kHz（24h）
Frequency stability：<1×10^-11(1000s）
◆Beat phase/frequency locking module
Beat phase/frequency locking module is used for frequency locking of multi-lasers. PreciLasers has launched a frequency control system for dual-channel 780nm laser device which serves as the laser source of ⁸⁷Rb gravimeter and gradiometer. Frequency of channel1 is locked to the resonance peak with MTS-locking while channel2 is locked 6.834GHz offset from channel1 with beat phase locking. This dual-channel laser can offer almost all the laser that is needed for a ⁸⁷Rb gravimeter.

Error signal and output signal in Preci-Beat software

Beat phase/frequency locking is realized with Preci-Beat controller. A fast PD measures the beat signal between two lasers and the PFD module in Preci-Beat generates error signal with the beat signal and a reference signal, the laser frequency will then be locked by PID module.

The 3.4 GHz beat signal from two 1560nm lasers

 

For ⁸⁷Rb atom gravimeter, frequency chirping or jumping of laser is needed. A typical example is the Raman lasers whose frequency need to change within 3 pulses to compensate the doppler effect. Preci-Beat provides frequency jumping function with a switching time below 10 μs.