CN105180916A - Method for detecting atom spin precession of SERF (spin exchange relaxation free) atom spin gyroscope - Google Patents

Abstract

The invention provides a method for detecting atom spin precession of an SERF (spin exchange relaxation free) atom spin gyroscope. The atom spin precession is detected by a double-beam closed-loop electro-optical modulation detecting method. The atom spin precession, caused under the input condition of the external angular rate, of atoms in the spin SERF state is realized. According to the method provided by the invention, angular rate information carried by atom spin is extracted through the mutual action of linearly polarized light and atom spin precession, so that the measurement on the angular rate is realized. The detecting method provided by the invention has the advantages that the influence of scale factors such as light intensity and modulation amplitude can be effectively isolated; the influence of errors existing in the practical application on the precision of a detecting system can also be isolated in the theory aspect, so that the sensitivity is higher; the measurement precision of the SERF atom spin gyroscope is integrally and effectively improved.

Description

A kind of detection method of SERF atomic spin gyroscope atomic spin precession

Technical field

The present invention relates to a kind of detection method of SERF atomic spin gyroscope atomic spin precession, belong to photoelectric detection technology field.

Background technology

Spin is the intrinsic attribute of material, and atomic spin is made up of electron spin and nuclear spin.Atomic spin has angular momentum, and for an atomic spin assemblage, the synthesis of these angular momentums has gyroscopic inertia in inertial space, similar with the gyroscopic inertia of the high speed rotor in rotor gyro in inertial space.Therefore, atomic spin is utilized can to carry out the measurement of angular motion.2005, the researchist of Princeton College Physics system chanced on a kind of novel atomic spin gyroscope, utilized the sensitive volume of spheroid achieves 2 × 10 ^-3°/h ^1/2random walk, 4 × 10 ^-2°/drift of h.By theoretical analysis, by technological improvement under same sensitive volume, the gyrostatic performance of this atomic spin can obtain the raising of the order of magnitude, show that this novel atomic spin gyroscope has the feature of superhigh precision, small size.This gyroscope has fully utilized the electron spin of alkali metal atom and the nuclear spin of inert gas, work in without spin-exchange relaxation (SpinExchangeRelaxationFree-SERF) state by the electron spin manipulating alkali metal atom, the nuclear spin of intert-gas atoms and the electron spin strong coupling of alkali metal atom, carry out the measurement of angular motion, be called the atomic spin gyroscope based on SERF or SERF atomic spin gyroscope.

The atom realizing spin SERF state can cause the precession of atomic spin under the input of extraneous angular speed, extracts by linearly polarized light and the interaction of atomic spin precession the angular rate information that atomic spin carries, thus the measurement of realization to angular speed.Therefore, the detection method of SERF atomic spin gyroscope atomic spin precession becomes one of gordian technique.The detection of atomic spin precession finally can be mapped as the plane of polarization roll angle inspection of linear polarization detection laser.At present, for the linearly polarized light angle detection method of ultra-high sensitive SERF atomic spin gyroscope, SERF atom magnetometer, three kinds are mainly comprised: differential polarization method, Faraday modulation method and electro-optic modulation method.

Differential polarization method is owing to lacking modulating action, and when atom to be measured Spin precession angle is low frequency signal, the noises such as the 1/f of detection system are comparatively large, and the signal to noise ratio (S/N ratio) of system is poor.Although Faraday modulation method has highly sensitive advantage, also bring constant multiplier simultaneously and need the difficult points such as precise and stable, and the modulation amplitude that Faraday modulation device produces adopts power amplifier by current load on Faraday modulation coil, drives faraday's crystal to obtain by alternating magnetic field.This method makes to produce higher temperature and larger magnetic field in measure loop, brings difficulty to the accurate control in temperature and magnetic field.Electro-optic modulation method and Faraday modulation method similar, adopt electrooptical modulation replace Faraday modulation, system export in still comprise light intensity and these constant multipliers of modulation amplitude, need to carry out accurate closed-loop control to improve the precision of detection system to them.But the modulation amplitude that electrooptic modulator produces is carried on electro-optic crystal by the output voltage of voltage amplifier and obtains, and makes electrooptic modulator additionally not produce higher temperature and larger magnetic field compared to Faraday modulation device.In addition, also there is following error in actual applications: the optical axis mutual alignment of the polarizer and analyzer affects by mechanical deformation etc. and drifts about, and there is non-normal angle, is defined as γ; The magneto-optic effect of optical element can produce error corner, is defined as ε; The disturbance of air-flow, the change of temperature can change the air refraction detected near light path, cause the plane of polarization of linearly polarized light to rotate, are defined as τ.

Summary of the invention

The object of the invention is the deficiency in order to solve above-mentioned three kinds of detection methods, a kind of detection method of SERF atomic spin gyroscope atomic spin precession is provided, the method adopts twin-beam closed loop photoelectricity method for modulation detection, not only effectively can isolate the impact of above-mentioned constant multiplier, the impact of above-mentioned error on detection system precision can also be isolated in principle.

The technical solution used in the present invention is: a kind of detection method of SERF atomic spin gyroscope atomic spin precession, comprises the following steps:

(1) detection laser is divided into the two-beam of exiting parallel by beam splitter and catoptron, and after the same polarizer, initial beam intensity is respectively I _o1and I _o2;

(2) this two bundles detection laser is by same 1/4 slide and electrooptic modulator, and this modulator is driven by lock-in amplifier and voltage amplifier, and modulating frequency is ω, modulation amplitude is A;

A branch of incident alkaline metal air chamber in (3) two bundle detection laser, interact with atomic spin precession and produce rotational angle theta, another Shu Buyu alkaline metal air chamber is had an effect;

(4), after step (3), two bundle detection laser are by same 1/4 slide and closed loop electric light actuator, and this actuator produces corner α to two bundle detection laser ₁;

(5) through the detection laser of alkaline metal air chamber separately through second 1/4 slide and closed loop electric light actuator, obtain corner α ₂;

(6) adopt same analyzer to carry out the analyzing of signal, through two bundle detection laser of analyzer, absorbed by two photodetectors respectively and obtain light intensity I ₁and I ₂;

(7) the above-mentioned signal of lock-in amplifier demodulation obtains I respectively _{ω 1}and I _{ω 2};

(8) PID controller 1 and PID controller 2 couples of I are adopted respectively _{ω 1}and I _{ω 2}carry out closed-loop control, make these parameters remain zero; The control angle α obtained by PID controller 2 ₂, be the final output of detection system.

As preferably, the modulation amplitude that described electrooptic modulator produces is carried on electro-optic crystal by the output voltage of voltage amplifier and obtains, and makes electrooptic modulator additionally not produce higher temperature and larger magnetic field.Therefore, electrooptical modulation detection method reduces realizing complexity and controlling difficulty of system, is conducive to the integrated of system and miniaturization.

As preferably, the Electrooptic crystal material that described electrooptic modulator selects delustring smaller.The extinction ratio of electro-optic crystal can be introduced constant value and be biased, and is proportional to the size of extinction ratio, very little on the measurement range impact of photodetector when constant value is biased less, ensure that the sensitivity of photodetector.

Beneficial effect: the present invention detects the gyrostatic atomic spin precession of SERF atomic spin by twin-beam closed loop photoelectricity method for modulation detection, not only effectively can isolate the impact of constant multiplier, the error that exists in practical application can also be isolated on the impact of detection system precision in principle.Therefore this detection method has higher sensitivity, can effectively improve the gyrostatic measuring accuracy of SERF atomic spin on the whole.

Accompanying drawing explanation

Fig. 1 is the gyrostatic General Principle schematic diagram of SERF atomic spin;

Fig. 2 is twin-beam closed loop electrooptical modulation detection method principle schematic;

Fig. 3 is the SERF atomic spin gyroscope experimental provision schematic diagram based on twin-beam closed loop electrooptical modulation detection method.

Embodiment

Below in conjunction with the drawings and specific embodiments, the present invention is further illustrated.

Fig. 1 is the gyrostatic General Principle schematic diagram of SERF atomic spin.Pumping light to polarize alkali metal atom along Z-direction, and the detection laser along X-axis detects the atomic spin precession that atom causes under the input of y-axis deflection speed.Namely the gyrostatic sensitive axes of SERF atomic spin is the direction of vertical drive and detection laser plane.

The detection method of a kind of SERF atomic spin gyroscope atomic spin precession that the present invention proposes, its Cleaning Principle schematic diagram as shown in Figure 2, primarily of compositions such as the polarizer, analyzer, 1/4 slide and electrooptic modulator, photodetector, lock-in amplifier, voltage amplifier, PID controller.

First, detection laser is divided into the two-beam of exiting parallel by beam splitter and catoptron, and after the same polarizer, initial beam intensity is respectively I _o1and I _o2; This two bundles detection laser is by same 1/4 slide and electrooptic modulator, and this modulator is driven by lock-in amplifier and voltage amplifier, and modulating frequency is ω, modulation amplitude is A; A branch of incident alkaline metal air chamber in two bundle detection laser, interact with atomic spin precession and produce rotational angle theta, another Shu Buyu alkaline metal air chamber is had an effect; Afterwards, two bundle detection laser are by same 1/4 slide and closed loop electric light actuator, and this actuator produces corner α to two bundle detection laser ₁; Through the detection laser of alkaline metal air chamber separately through second 1/4 slide and closed loop electric light actuator, obtain corner α ₂; Adopt same analyzer to carry out the analyzing of signal, through two bundle detection laser of analyzer, absorbed by two photodetectors respectively and obtain light intensity I ₁and I ₂;

$\begin{array}{c}{I}_1=I_0\·{\sin }^2\left(A\cos \mathrm{\ω}t+{\mathrm{\α}}_1+\mathrm{\γ}+\mathrm{\ϵ}+\mathrm{\τ}\right)\\ I_2=I_0\·{\sin }^2(Acos\mathrm{\ω}t+\mathrm{\θ}+{\mathrm{\α}}_1+{\mathrm{\α}}_2+\mathrm{\γ}+\mathrm{\ϵ}+\mathrm{\τ})\end{array}---\left(1\right)$

Work as α ₁+ γ+ε+τ, θ+α ₁+ α ₂when+γ+ε+τ is all less with the amplitude of A, formula (1) can be reduced to:

$\begin{array}{c}{I}_1\≈I_0\·{\left(A\cos \mathrm{\ω}t+{\mathrm{\α}}_1+\mathrm{\γ}+\mathrm{\ϵ}+\mathrm{\τ}\right)}^2\\ I_2\≈I_0\·{(Acos\mathrm{\ω}t+\mathrm{\θ}+{\mathrm{\α}}_1+{\mathrm{\α}}_2+\mathrm{\γ}+\mathrm{\ϵ}+\mathrm{\τ})}^2\end{array}---\left(2\right)$

By the signal receiving of lock-in amplifier, can extract in the output signal I of photodetector, frequency is the amplitude size of ω:

$\begin{array}{c}{I}_{\mathrm{\ω}1}\≈2I_{0}A({\mathrm{\α}}_1+\mathrm{\γ}+\mathrm{\ϵ}+\mathrm{\τ})\\ I_{\mathrm{\ω}2}\≈2I_{0}A(\mathrm{\θ}+{\mathrm{\α}}_1+{\mathrm{\α}}_2+\mathrm{\γ}+\mathrm{\ϵ}+\mathrm{\τ})\end{array}---\left(3\right)$

By the I that lock-in amplifier exports _ωsignal input PID controller, thus the corner α that Control loop electric light actuator produces.In formula (3), I _ωabout the linear function that α is a zero crossing.Therefore, control corner α by PID controller, make the output I of lock-in amplifier _ωremain zero.The output expression formula obtaining two PID controller is respectively:

$\begin{array}{c}{\mathrm{\α}}_1=-(\mathrm{\γ}+\mathrm{\ϵ}+\mathrm{\τ})\\ {\mathrm{\α}}_2=-(\mathrm{\θ}+{\mathrm{\α}}_1+\mathrm{\γ}+\mathrm{\ϵ}+\mathrm{\τ})\end{array}---\left(4\right)$

By the α in formula (4) ₁bring α into ₂, now, the corner α that rotational angle theta to be measured is produced by closed loop electric light actuator ₂read,

That is:

α ₂＝-θ(5)

This formula is the atomic spin precession signal that detection system will obtain.Can see from formula (5), Output rusults is only relevant with treating angle measurement θ, and and I ₀, the drift such as A, γ, ε, τ is no longer relevant, thus the drift having isolated above-mentioned parameter in principle is on the impact of detection system precision.

Fig. 3 is the SERF atomic spin gyroscope experimental provision schematic diagram based on twin-beam closed loop electrooptical modulation detection method.Beam composition is detected primarily of alkaline metal air chamber, heating air chamber, magnetic shielding bucket, magnetic compensation coil, optical pumping beam and light.Alkaline metal air chamber is heated by thermal current (or electric current) as without in the stove of magnetic, and heating furnace periphery is three-dimensional active magnetic compensating coil, and device realizes magnetic shielding by four layers of cylindrical magnetics shielding bucket.Pumping laser along Z-direction, detection laser along X-direction, the angular speed of responsive Y-axis.

Below by reference to the accompanying drawings embodiments of the present invention are described in detail, but the present invention is not limited to described embodiment.For those of ordinary skill in the art, in the scope of principle of the present invention and technological thought, embodiment is carried out to these embodiments and carries out multiple change, amendment, replacement and distortion and still fall within the scope of protection of the present invention.

Claims (3)

1. a detection method for SERF atomic spin gyroscope atomic spin precession, is characterized in that: comprise the following steps:

(1) detection laser is divided into the two-beam of exiting parallel by beam splitter and catoptron, and after the same polarizer, initial beam intensity is respectively I ₀₁and I ₀₂;

(2) this two bundles detection laser is by same 1/4 slide and electrooptic modulator, and this modulator is driven by lock-in amplifier and voltage amplifier, and modulating frequency is ω, modulation amplitude is A;

A branch of incident alkaline metal air chamber in (3) two bundle detection laser, interact with atomic spin precession and produce rotational angle theta, another Shu Buyu alkaline metal air chamber is had an effect;

(4), after step (3), two bundle detection laser are by same 1/4 slide and closed loop electric light actuator, and this actuator produces corner α to two bundle detection laser ₁;

(5) through the detection laser of alkaline metal air chamber separately through second 1/4 slide and closed loop electric light actuator, obtain corner α ₂;

(6) adopt same analyzer to carry out the analyzing of signal, through two bundle detection laser of analyzer, absorbed by two photodetectors respectively and obtain light intensity I ₁and I ₂;

(7) the above-mentioned signal of lock-in amplifier demodulation obtains I respectively _{ω 1}and I _{ω 2};

(8) PID controller 1 and PID controller 2 couples of I are adopted respectively _{ω 1}and I _{ω 2}carry out closed-loop control, make these parameters remain zero; The control angle α obtained by PID controller 2 ₂, be the final output of detection system.

2. the detection method of a kind of SERF atomic spin gyroscope atomic spin precession according to claim 1, it is characterized in that: the modulation amplitude that described electrooptic modulator produces is carried on electro-optic crystal by the output voltage of voltage amplifier and obtains, and makes electrooptic modulator additionally not produce higher temperature and larger magnetic field.

3. the detection method of a kind of SERF atomic spin gyroscope atomic spin precession according to claim 1, is characterized in that: the Electrooptic crystal material that described electrooptic modulator selects delustring smaller.