CN104834149B - Single fiber type CARS excitation source apparatus and implementation method based on the non-linear tuning of twin-stage - Google Patents

Abstract

The invention discloses a single-fiber CARS excitation source device and method based on dual-stage nonlinear tuning, including a femtosecond fiber laser light source, an electronically controlled optical power attenuator, a primary tuner, a pulse stretcher, and a secondary tuner , pump laser, wavelength division multiplexer, gain fiber, filter and output port. The femtosecond fiber laser source outputs femtosecond pulses as Stokes optical pulses, which enter the electronically controlled optical power attenuator, and realize power-controlled optical pulse wavelength tuning in the first-level tuner. After being stretched into picosecond pulses by the pulse stretcher Enter the gain fiber to amplify, and generate signal light pulse and idler light pulse in the secondary tuner. The signal light pulse is used as the pump light pulse of the CARS source, and the filter filters out the idler light pulse and the residual pump continuous light , the output port output. Compared with the prior art, the present invention adopts a single-fiber optical path structure and electronically controlled tuning, has the advantages of compact structure, anti-interference, high reliability and fast tuning speed, and meets the needs of CARS fast imaging.

Description

Single-fiber CARS excitation source device and implementation method based on dual-stage nonlinear tuning

technical field

The invention relates to the technical field of optical nonlinear microscopic imaging, in particular to an excitation source device of a CARS microscopic imaging system.

Background technique

CARS microscopy utilizes coherent anti-Stokes Raman scattering to detect molecules. When the frequency difference between the pump light and the Stokes light is equal to the vibration frequency of the molecule to be detected, strong anti-Stokes scattered light will be generated, thereby enabling the detection of the molecule to be detected. Due to the high signal-to-noise ratio of CARS microscopic imaging technology, its three-dimensional tomographic capability, and the need for fluorescent labeling and confocal systems, it has attracted widespread attention in recent years and has developed rapidly. The CARS microscopy imaging system requires two wavelengths of laser light, at least one of which is wavelength tunable. At present, CARS systems usually use two Ti-doped sapphire lasers with feedback control or two optical parametric oscillators pumped by the same pump source as the excitation source. The pump light and the Stokes light need to be synchronized, and the adjustment is complicated and requires The tuning of the mechanical device leads to slow wavelength tuning, and the entire system is huge, requiring full-time technicians to maintain it, which seriously hinders the wide application of CARS. Therefore, a compact, low-cost, high-reliability and easy-to-use CARS excitation source is very important.

Contents of the invention

Aiming at the problems existing in the traditional CARS device, the present invention proposes a single-fiber CARS excitation source device and method based on dual-stage nonlinear tuning. The CARS excitation source integrates the soliton self-frequency shift and four-wave mixing effect. First, the electronic control system is used to adjust the optical power to achieve wavelength tuning in a small range, and then the nonlinear effect is used to realize simultaneous dual-wavelength generation and wide-range tuning. system compactness and high reliability.

The present invention proposes a single-fiber CARS excitation source device based on dual-stage nonlinear tuning. The device includes femtosecond fiber laser light source 1, electronically controlled optical power attenuator 2, voltage controller 3, Primary tuner 4, pulse stretcher 5, pump laser source 6, wavelength division multiplexer 7, gain fiber 8, secondary tuner 9, optical filter 10 and output port 11; where:

The femtosecond fiber laser light source 1 is used to provide femtosecond-level linearly polarized pulsed light, which is used as the Stokes light pulse seed source of the CARS source. The pulse width range is 50-200fs, and the center wavelength is 1030-1064nm. Frequency 10MHz～100MHz, pulse energy greater than 1nJ;

The electronically controlled optical power attenuator 2 is composed of a phase retarder and a polarizer, and is used to apply a voltage to the phase retarder to change the phase delay between the horizontal polarization and the vertical polarization, so that the polarization state of the outgoing light changes, and the transmission The power of the polarizer changes to realize the adjustment of optical power attenuation;

The voltage controller 3 is used to output a control voltage to control the attenuation value of the electronically controlled optical power attenuator;

The primary tuner 4 is composed of a photonic crystal fiber, and is used for small-scale wavelength tuning of femtosecond pulsed light, with a tuning range of 10-40nm and a tuning wavelength range of 10-40nm;

The pulse stretcher 5 is composed of single-mode and multi-mode fiber fusion splices, and is used to stretch the Stokes optical pulse to 30-80ps;

The pump laser source 6 adopts a 980nm pump laser for providing pumping continuous light to the gain fiber;

The wavelength division multiplexer 7 synthesizes the pump continuous light and the Stokes light pulse output by the first-level tuner into one bundle, and inputs it into the gain fiber;

Gain fiber 8, using ytterbium-doped fiber, is used to amplify the Stokes optical pulse after the first-level tuner, so that the output pulse peak power is 3-20kW;

The secondary tuner 9 is composed of a photonic crystal fiber, which is tuned by the four-wave mixing effect of the photonic crystal fiber; the output of the primary tuner 4 and the amplified high peak power Stokes light pulse are injected into its photon After the crystal fiber, the signal light pulse and the idler light pulse are generated by four-wave mixing; the wavelength of the signal light pulse and the idler light pulse depends on the wavelength of the injected Stokes light pulse; the signal light pulse is used as the CARS source Small-scale tuning of pump light pulse and Stokes light pulse wavelength will lead to large-scale tuning of signal light pulse; the frequency difference between pump light pulse and Stokes light pulse of CARS source covers the range of 400-4000cm ^-1 range of the molecular vibration spectrum.

The optical filter 10 is used to filter out the idler light pulse of the secondary tuner and the remaining pumping continuous light output by the pumping laser;

Output port 11, external optical fiber interface for output.

The present invention also proposes a method for realizing a single-fiber CARS excitation source device based on dual-stage nonlinear tuning. The method includes the following steps:

The femtosecond fiber laser source 1 provides femtosecond-level linearly polarized pulsed light, which is used as the Stokes light pulse seed source of the CARS source. The pulse width ranges from 50 to 200 fs, the center wavelength is 1030 to 1064 nm, and the repetition frequency is 10 MHz to 100 MHz. Pulse energy greater than 1nJ;

The voltage controller 3 outputs a control voltage, thereby controlling the attenuation value of the electronically controlled optical power attenuator 2 composed of a phase retarder and a polarizer, and realizing adjustment of optical power attenuation;

Control the injected optical power of the primary tuner 4 to realize the tuning of Stokes optical pulses, and the tuning wavelength range is 10-40nm;

The pulse stretcher 5 stretches the Stokes light pulse to 30-80ps;

The pump laser 6 provides pumping continuous light to the gain fiber;

The pump continuous light and the Stokes light pulse output by the primary tuner are synthesized into one bundle by the wavelength division multiplexer 7, and then input into the gain fiber for amplification, and the Stokes light pulse tuned by the primary tuner 4 The output pulse peak power after amplification is 3~20kW;

The output optical pulse is injected into the secondary tuner 9, and the four-wave mixing effect of the photonic crystal fiber is used to generate the signal optical pulse and the idler optical pulse. The wavelengths of the signal optical pulse and the idler optical pulse depend on the injected Stokes light The pulse wavelength, the signal light pulse is used as the pump light pulse of the CARS source, the small-scale tuning of the Stokes light pulse wavelength will cause the large-scale tuning of the signal light pulse, the frequency difference between the Stokes light pulse and the signal light pulse Covering the range of molecular vibration spectrum from 400 to 4000cm ^-1 ;

After the idler light of the secondary tuner and the pumping light output by the pumping laser are filtered out by the optical filter 10 , optical pulses of two wavelengths are output through the output port 11 .

Compared with the prior art, the present invention has the following technical effects:

1. The single-fiber CARS excitation source device based on dual-stage nonlinear tuning proposed by the present invention has a simple structure, only a single-fiber optical path, no need for beam splitting and delay adjustment parts, and the entire system has no mechanical moving parts, greatly improving reliability and stability improve;

2. The two-stage tuning structure effectively reduces the difficulty of implementing a wide tuning range, and expands the molecular vibration wavenumber range covered by the CARS source. The electronically controlled tuning speed is fast and has natural pulse synchronization, which is conducive to the realization of CARS real-time imaging.

Description of drawings

Figure 1 is a structural diagram of a single-fiber CARS excitation source system based on dual-stage nonlinear tuning;

Fig. 2 is a graph showing the variation of the wavelength of the signal light pulse and the idler light pulse with the wavelength of the injected Stokes light pulse in the secondary tuner;

Fig. 3 is the spectrogram of signal light and idler light after Stokes light pulse injection;

In the figure, 1. femtosecond fiber laser source, 2. electronically controlled optical power attenuator, 3. voltage controller, 4. primary tuner, 5. pulse stretcher, 6. pump laser source, 7. wavelength division Multiplexer, 8, gain fiber, 9, secondary tuner, 10, optical filter, 11, output port.

detailed description

The technical solution of the present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

Implementation example 1: A single-fiber CARS excitation source device based on dual-stage nonlinear tuning

As shown in Figure 1, the device includes a femtosecond fiber laser source 1, an electronically controlled optical power attenuator 2, a voltage controller 3, a primary tuner 4, a pulse stretcher 5, a pump laser source 6, a wavelength division multiplexing 7, gain fiber 8, secondary tuner 9, optical filter 10 and output port 11.

The femtosecond linearly polarized pulsed light output by the femtosecond fiber laser source 1 enters the electronically controlled optical power attenuator 2 as a Stokes optical pulse seed source, and the optical power attenuation value is controlled by the voltage controller 3, and the optical pulse after optical power attenuation Entering the primary tuner 4 to realize power-controlled optical pulse wavelength tuning, the output pulsed light is stretched by the pulse stretcher 5, and then combined with the pumped continuous light output by the pumping laser source 6 in the wavelength division multiplexer 7 and enters to the gain fiber 8, and enter the secondary tuner 9 after amplification to generate signal light pulses and idler light pulses, the optical filter 10 filters out the idler light pulses and the remaining pumped continuous light, and outputs the signal light at the output port 11 pulses and Stokes light pulses.

Implementation example 2: A method for realizing a single-fiber CARS excitation source based on dual-stage nonlinear tuning

Using femtosecond fiber laser light source to provide femtosecond level linearly polarized pulse light, used as the Stokes light pulse seed source of CARS source, the pulse width range is 50-200fs, the center wavelength is 1030-1064nm, and the repetition frequency is 10MHz-100MHz. Pulse energy greater than 1nJ. The voltage controller outputs the control voltage to control the attenuation value of the electronically controlled optical power attenuator composed of the phase retarder and the polarizer to realize the optical power attenuation adjustment. The primary tuner is composed of photonic crystal fiber. By controlling the injected light power, the soliton self-frequency shift nonlinear effect of photonic crystal fiber is used to realize the tuning of Stokes optical pulse, and the tuning wavelength range is 10-40nm. The pulse stretcher is composed of single-mode and multi-mode fiber fusion, which can stretch the Stokes optical pulse to 30-80ps. The 980nm pump laser provides pumping continuous light to the gain fiber. The pumping continuous light and the Stokes light pulse output by the first-stage tuner are synthesized into one beam through a wavelength division multiplexer, and then input into the gain fiber for amplification. The first-stage The Stokes optical pulse tuned by the tuner is amplified and the output pulse peak power is 3-20kW. The output optical pulse is injected into the secondary tuner composed of photonic crystal fiber, and the four-wave mixing effect of photonic crystal fiber is used to generate signal optical pulse and idler optical pulse. The wavelength of signal optical pulse and idler optical pulse depends on the injected The Stokes light pulse wavelength, the signal light pulse is used as the pump light pulse of the CARS source, and the small-scale tuning of the Stokes light pulse wavelength will cause the large-scale tuning of the signal light pulse. The frequency difference between the Stokes light pulse and the signal light pulse covers the range of the molecular vibration spectrum in the range of 400-4000 cm ⁻¹ . After filtering out the idler light used for filtering out the secondary tuner and the pumping light output by the pumping laser with an optical filter, the optical pulses of two wavelengths are output through the output port.

As shown in Figure 2, when the peak power of the Stokes light pulse injected into NKT's LMA-8 photonic crystal fiber is 3kW, the wavelength of the signal light pulse and idler light pulse varies with the wavelength of the Stokes light pulse.

As shown in FIG. 3 , it is a spectrum diagram of signal light and idler light generated after Stokes light pulse injection. The signal light pulse is used as the pump light pulse of the CARS source, and the small range tuning of the Stokes light pulse wavelength will lead to the large range tuning of the signal light pulse. The frequency difference between the Stokes light pulse and the signal light pulse covers the range of the molecular vibration spectrum in the range of 400-4000 cm ⁻¹ . After the idler light used for filtering out the secondary tuner and the pump light output by the pump laser are filtered by the optical filter 10, the light pulses of two wavelengths of the CARS excitation source are output through the output port 11.

Implementation Example 3: Application Example

The CARS source outputs a signal light pulse and a Stokes light pulse, wherein the signal light pulse is used as a pump light pulse of the CARS source. Under the action of the pump light pulse of the CARS source and the two light pulses of the Stokes light pulse, the molecular vibration in the analyte that resonates with the frequency difference between the pump light pulse and the Stokes light pulse is first excited, so that It generates resonance, and then the resonant molecular vibration converts a large amount of pump light output by the CARS source into anti-Stokes light to realize the detection of specific molecules. Through two-stage tuning, the pump light pulses and Stokes light pulses of the CARS source cover molecular vibrations with wavenumbers from 400 to 4000 cm ^-1 , thus satisfying the measurement of molecular vibrational spectra and excitation imaging of specific molecules in biochemistry.

Claims (2)

1. a kind of single fiber type CARS excitation source apparatus based on the non-linear tuning of twin-stage, it is characterised in that the device is from being input to Output sequentially includes femtosecond fiber LASER Light Source (1), automatically controlled optical power attenuation device (2), voltage controller (3), one-level tuner (4), pulse stretcher (5), pump laser source (6), wavelength division multiplexer (7), gain fibre (8), two grades of tuners (9), optical filterings Device (10) and output port (11)；Wherein：

The femtosecond fiber LASER Light Source (1), for providing femtosecond linear polarization pulsed light, the stokes light as CARS sources Pulse seed source, 50~200fs of its pulse duration range, centre wavelength be 1030~1064nm, repetition rate 10MHz~100MHz, Pulse energy is more than 1nJ；

The automatically controlled optical power attenuation device (2), is made up of phase delay device and analyzer, for applying a voltage to phase delay Device changes the phase delay between horizontal polarization and vertical polarization, the polarization state of emergent light is changed, through analyzer Power produces change, realizes that optical power attenuation is adjusted；

The voltage controller (3), for output control voltage, controls the pad value of automatically controlled optical power attenuation device；

The one-level tuner (4), is made up of photonic crystal fiber, for realizing that the wavelength of small range is adjusted to femtosecond pulse light It is humorous, 10~40nm of tuning range；

The pulse stretcher (5), is made up of single mode and multimode fibre welding, for by Stokes optical pulse broadening to 30~ 80ps；

The pump laser source (6), using 980nm pump lasers, for providing the continuous light of pumping to gain fibre；

The wavelength division multiplexer (7), the continuous light of pumping and one-level tuner output stokes light pulse combination is a branch of, input Into gain fibre；

Gain fibre (8), using Yb dosed optical fiber, for amplifying the Stokes light pulse after one-level tuner, makes output pulse Peak power is in 3~20kW；

Two grades of tuners (9), are made up of photonic crystal fiber, are acted on and tuned using the four-wave mixing of photonic crystal fiber； One-level tuner (4) is exported and after the high-peak power stokes light impulses injection photonic crystal fiber of amplified formation, Signal pulse and ideler frequency light pulse are produced by four-wave mixing effect；Signal pulse and the wavelength of ideler frequency light pulse are depended on The Stokes light pulse wavelength of injection；Signal pulse is used as the pumping light pulse in CARS sources, Stokes light pulse wavelength Small range tuning will cause a wide range of tuning of signal pulse；The pumping light pulse in CARS sources and Stokes light pulse Frequency difference covers 400~4000cm^-1The molecular vibration spectral limit of scope；

The filter (10), the pumping that ideler frequency light pulse and remaining pump laser for filtering out two grades of tuners are exported Continuous light；

Output port (11), the external fiber interface for output.

2. a kind of realization side of the single fiber type CARS excitation source apparatus based on the non-linear tuning of twin-stage as claimed in claim 1 Method, it is characterised in that this method comprises the following steps：

Femtosecond fiber LASER Light Source (1) provides femtosecond linear polarization pulsed light, the stokes light pulse seed as CARS sources Source, 50~200fs of its pulse duration range, centre wavelength is 1030~1064nm, repetition rate 10MHz~100MHz, pulse energy More than 1nJ；

Voltage controller (3) output control voltage, so as to control the automatically controlled luminous power being made up of phase delay device and analyzer to decline Subtract the pad value of device (2), realize that optical power attenuation is adjusted；

One-level tuner (4) injected optical power is controlled, is realized to stokes light Pulse tuning, tuning wavelength scope 10~ 40nm；

Pulse stretcher (5) is by Stokes optical pulse broadening to 30~80ps；

Pump laser (6) provides the continuous light of pumping to gain fibre；

It is by wavelength division multiplexer (7) that the continuous light of pumping and one-level tuner output stokes light pulse combination is a branch of, it is input to It is amplified in gain fibre, the amplified output peak value of pulse work(of the Stokes light pulse after one-level tuner (4) tuning Rate is in 3~20kW；

Output optical pulse is injected into two grades of tuners (9), and flashlight arteries and veins is produced using the four-wave mixing effect of photonic crystal fiber Stokes light pulse wavelength of the wavelength of punching and ideler frequency light pulse, signal pulse and ideler frequency light pulse dependent on injection, letter Number light pulse is used as the pumping light pulse in CARS sources, and the small range tuning of Stokes light pulse wavelength will cause signal pulse A wide range of tuning, the frequency difference of Stokes light pulse and signal pulse covers 400~4000cm^-1The molecular vibration spectrum of scope Scope；

Filtered out using filter (10) after the ideler frequency light of two grades of tuners and the pump light of pump laser output, through output port (11) light pulse of two wavelength is exported.