CN101900575B - An optical sensor based on an active resonant cavity and a cascaded passive resonant cavity - Google Patents

Abstract

The invention discloses an optical sensor based on an active resonant cavity and a passive resonant cavity cascaded therewith. At least one active resonant cavity with internal gain capable of emitting equally spaced comb-shaped spontaneous emission spectrum or laser spectrum, one passive resonant cavity with equally spaced comb-shaped filtering spectrum, and an optical receiver are included. The spectrum emitted by the active resonant cavity is input to the passive resonant cavity, and after being filtered by the passive resonant cavity, the emitted light is received by the optical receiver. The passive resonant cavity is provided with a sensing area whose optical length can be changed with the change of the external environment. The invention uses a low-cost multi-mode active resonant cavity as an input light source. When the optical lengths of the two cavities are the same, it is only necessary to simply measure the change of the output light intensity with an optical power detector to obtain the change of the measured physical quantity, which is easy to test and low in cost; when the optical lengths of the two cavities are different, the external The spectrometer can also expand the measurement range and improve the test accuracy.

Description

An optical sensor based on an active resonant cavity and a cascaded passive resonant cavity

technical field

The invention relates to an optical sensor, in particular to an optical sensor based on an active resonant cavity and a passive resonant cavity cascaded with it.

Background technique

As an important branch of information science and technology, optical sensing technology has very important applications in industrial process control, environmental monitoring, food safety and national security. Optical sensing technology can solve the problems of low sensitivity, susceptibility to interference, long sensing time and unsafe detection of certain chemical gases in electrical sensing technology. Optical sensors have the advantages of high sensitivity, small size, strong anti-electromagnetic interference ability, easy integration, and online detection, and they occupy an increasingly important position in the sensing field.

The basic principle of the optical waveguide sensor device is based on the evanescent wave that appears on the interface/surface of the optical fiber or planar waveguide. Since the evanescent wave penetrates the surface of the waveguide (contacting the substance to be measured) and returns to the waveguide, it affects the light transmitted in the waveguide. , so detecting changes in the transmitted light in the waveguide enables photo-sensing.

As shown in Figure 1, K. De Vos et al. in the literature "Silicon-on-Insulat or microring resonator forsensitive and label-free biosensing", Optics Express 15, pp.7610-7615 (2007). In the paper, the scheme of using the ring resonator as the optical waveguide sensor is proposed. The ring resonator is a kind of optical resonant cavity. Because it has a relatively sharp filtering line and is used as a sensor with high sensitivity, it has received extensive attention. The disadvantage of the K.De Vos et al. scheme is that an expensive spectrometer is needed to measure the wavelength shift of the transmission peak, and its measurement accuracy is directly related to the accuracy of the spectrometer. If the method of measuring the energy change of a fixed wavelength near the transmission peak is used, a single-mode laser with a narrow linewidth is required as the light source, and the wavelength of the laser must have a precise relative position with the transmission peak of the resonant ring, and it must be highly stable. . These requirements greatly increase the cost of the measurement device and reduce reliability.

Contents of the invention

In view of the deficiencies in the background technology, the object of the present invention is to provide an optical sensor based on an active resonant cavity and a passive resonant cavity cascaded therewith.

The technical scheme that the present invention adopts is as follows:

Technical solution 1:

The invention includes an active resonant cavity capable of emitting equally spaced comb-shaped spontaneous radiation spectrum or laser spectrum with internal gain, a passive resonant cavity with an equally spaced comb-shaped filter spectrum, and an optical power detector; the active resonant cavity and The optical length of the passive resonant cavity is the same, and there is at least a passive resonant cavity sensing area whose optical length can change with the external environment in the passive resonant cavity, and the spectrum emitted by an output port of the active resonant cavity is input to the wireless The source resonator is filtered by the passive resonator and then received by an optical power detector.

The active resonator is an active Fabry-Perot resonator, an active ring resonator or a multi-segment active resonator with a distributed feedback grating structure inside.

The passive resonator is a passive ring resonator, a passive Fabry-Perot resonator or a multi-segment passive resonator with a distributed feedback grating structure inside.

The active resonant cavity is an active resonant cavity that is applied with a microwave driving signal with the same cycle as that of photons in the active resonant cavity, so as to keep its emission spectrum free from external interference.

Another optical power detector is arranged at the other output port of the active resonant cavity.

Technical solution 2:

The invention includes an active resonant cavity capable of emitting equally spaced comb-shaped spontaneous emission spectrum or laser spectrum with internal gain, a passive resonant cavity with an equally spaced comb-shaped filter spectrum, and a spectrometer; the active resonant cavity and the passive resonator The optical length of the cavity is different. At least a section of the passive resonant cavity sensing area whose optical length can change with the external environment is provided in the passive resonant cavity. The spectrum emitted by an output port of the active resonant cavity is input to the passive resonant cavity. After being filtered by the passive resonant cavity, it is received by the spectrometer.

The active resonator is an active Fabry-Perot resonator, an active ring resonator or a multi-segment active resonator with a distributed feedback grating structure inside.

The passive resonator is a passive ring resonator, a passive Fabry-Perot resonator or a multi-segment passive resonator with a distributed feedback grating structure inside.

The active resonant cavity is an active resonant cavity that is applied with a microwave driving signal with the same cycle as that of photons in the active resonant cavity, so as to keep its emission spectrum free from external interference.

Compared with background technology, the beneficial effect that the present invention has is:

The present invention uses the filtering effect of the active-passive cascaded double resonant cavity. When the optical lengths of the active and passive resonant cavities are the same, it is only necessary to simply use an optical power detector to measure the change of the output light intensity in the full spectral range. The change of the measured physical quantity can be obtained, and it is no longer necessary to obtain spectral-related information through a spectrometer, reducing the cost of device testing, and using low-cost multi-mode active resonant cavities such as Fabry-Perot cavities as input light sources , reduce the cost of device production, and, through the integration technology of active and passive components, no external light source is needed, and the need for high-difficulty and high-cost sensing waveguide optical coupling is also eliminated. Furthermore, when the optical lengths of the active and passive resonators are different, the output spectra of the vernier effect of the two resonators can be obtained through the spectrometer, which can further expand the measurement range and improve the test accuracy. From the perspectives above, the cost of the light sensor of the present invention is greatly reduced compared with the traditional passive light sensor, and the use and test are easier.

Description of drawings

Fig. 1 is a schematic diagram of a passive optical waveguide sensor based on a single ring resonant cavity in the background art.

Fig. 2 is a schematic structural diagram of the first embodiment of the present invention.

Fig. 3 is the fluorescence emission spectrum of the active Fabry-Perot resonator and passive ring resonator when the optical path difference between the active Fabry-Perot resonator and the passive ring resonator is 0 Transmission spectrum of a ring resonator.

Fig. 4 is the fluorescence emission spectrum of the active Fabry-Perot resonator and the passive ring resonator when the optical path difference between the active Fabry-Perot resonator and the passive ring resonator in the first embodiment of the present invention is 0 Superposition results of ring resonator transmission spectra.

Fig. 5 is the fluorescence emission spectrum of the active Fabry-Perot resonator and passive Transmission spectrum of a ring resonator.

Fig. 6 is the superposition result of the fluorescence emission spectrum of the active resonator and the transmission spectrum of the passive resonator when the optical path difference between the active Fabry-Perot resonator and the passive ring resonator is non-zero in the first embodiment of the present invention .

Fig. 7 is a curve of the variation of the optical power detected by the optical power detector with the equivalent guide refractive index of the passive ring resonator wave in the first embodiment of the present invention.

Fig. 8 is a schematic structural diagram of the second embodiment of the present invention.

Fig. 9 is a schematic structural diagram of a third embodiment of the present invention.

Fig. 10 is a schematic structural diagram of a fourth embodiment of the present invention.

Fig. 11 is a schematic structural diagram of the fifth embodiment of the present invention.

Fig. 12 is a schematic structural diagram of the sixth embodiment of the present invention.

Figure 13 shows multiple longitudinal modes of an active Fabry-Perot resonator and a passive ring resonator. and the material gain spectrum of the active cavity.

Fig. 14 is the fluorescence emission spectrum of the active Fabry-Perot resonator and the transmission spectrum of the passive ring resonator when the refractive index of the passive ring resonator is 3.215 in the sixth embodiment of the present invention.

Fig. 15 is the superposition result of the fluorescence emission spectrum of the active Fabry-Perot resonator and the transmission spectrum of the passive ring resonator when the refractive index of the passive ring resonator is 3.215 in the sixth embodiment of the present invention.

Fig. 16 is the fluorescence emission spectrum of the active Fabry-Perot resonator and the transmission spectrum of the passive ring resonator when the refractive index of the passive ring resonator is 3.2155 in the sixth embodiment of the present invention.

Fig. 17 is the superposition result of the fluorescence emission spectrum of the Fabry-Perot resonator and the transmission spectrum of the passive ring resonator when the refractive index of the passive ring resonator is 3.2155 in the sixth embodiment of the present invention.

Fig. 18 is the superposition result of the fluorescence emission spectrum of the Fabry-Perot resonator and the transmission spectrum of the passive ring resonator when the spectrometer receives two modes with equal energy in the sixth embodiment of the present invention.

In the figure: 1. Active Fabry-Perot resonator, 2. Passive ring resonator, 3. An optical power detector, 11. Microwave drive with a period similar to that of photons in the active resonator Signal, 12, the first mirror of the active Fabry-Perot resonator, 13, the second mirror of the active Fabry-Perot resonator, 20, the passive waveguide area of the passive ring resonator, 21, Passive ring resonator sensing area, 22, first passive waveguide, 23, second passive waveguide, 4, passive Fabry-Perot resonator, 40, passive Fabry-Perot resonator Passive waveguide area, 41, passive Fabry-Perot resonator sensing area, 42, first mirror of passive Fabry-Perot resonator, 43, passive Fabry-Perot resonator The second reflection mirror, 5, the active ring resonant cavity, 51, the third passive waveguide, 6, another optical power detector, 7, the spectrometer.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Fig. 2 is the first implementation of the optical sensor based on the active resonant cavity and the passive resonant cavity cascaded with it according to the present invention. It includes at least one active Fabry-Perot resonator 1 with an equally spaced comb spectral output with internal gain and a passive ring resonator 2 with an equally spaced comb filter spectrum, and an optical power detection Device 3; the optical length of the active Fabry-Perot resonator is the same as that of the passive ring resonator, and a passive ring resonator sensor whose optical length can change with the external environment is set in the passive ring resonator Zone 21, the spectrum emitted by the active Fabry-Perot resonator is input to the passive ring resonator through the first passive waveguide 22, and after being filtered by the passive ring resonator, it is passed through the second passive waveguide 23 by a Received by the optical power detector 3.

In the figure, the active Fabry-Perot resonator is composed of the gain region and the first reflector 12 of the active Fabry-Perot resonator and the second reflection mirror 12 of the active Fabry-Perot resonator located at its two ends. Mirror 13 constitutes. Photons of spontaneous emission are amplified in the gain region, part of which is reflected back into the active cavity at the two mirrors 12 and 13 to continue to be amplified, and the other part passes through the second reflector of the active Fabry-Perot resonator 13 emerges to form a comb-like emission spectrum. The passive ring resonant cavity 2 is composed of a passive ring resonant cavity passive waveguide area 20 and a passive ring resonant cavity sensing area 21 . The spectrum emitted by the active Fabry-Perot resonator is filtered by the passive ring resonator and then received by the optical power detector. The passive ring resonator is respectively connected with the active Fabry-Perot resonator and the optical power detector through the first and second passive waveguides.

The optical power P monitored by the optical power detector can be expressed as:

$\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{<span\; class="notranslate">\; +</span><span\; class="notranslate">\; \&infin;</span>}{<span\; class="notranslate">\; \&Integral;</span>}}\mathrm{<span\; class="notranslate">\; I</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; d\&omega;</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Where I(ω) represents the emission spectrum of the active Fabry-Perot resonator 1, and T(ω) represents the filter spectrum of the passive ring resonator 2. Generally speaking, the emission spectrum linewidth of the active Fabry-Perot resonator 1 is much smaller than the filter spectrum of the passive ring resonator 2, so:

$\mathrm{<span\; class="notranslate">\; I</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>\underset{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; \&infin;</span>}{\overset{<span\; class="notranslate">\; +</span><span\; class="notranslate">\; \&infin;</span>}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\mathrm{<span\; class="notranslate">\; \&Delta;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Where ω _k =kπc/L ₁ is the kth resonant frequency of the active Fabry-Perot resonator 1 , c is the speed of light, and L ₁ is the optical length of the active Fabry-Perot resonator 1 . Δ(ω) is the impact function, F(ω) is the envelope of the emission spectrum, and ω _k0 is the peak frequency of the emission spectrum envelope.

For a passive ring resonator, its filter function can be expressed as:

$\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="0"\; label="T"\; filenames="HSA00000175780600022.png,HSA00000175780600031.png"\; state="\{\{state\}\}">T</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{<span\; class="notranslate">\; |</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; C</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="L"\; filenames="HSA00000175780600041.png,HSA00000175780600052.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; \&omega;</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; c</span>}}}<span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

where C is the through-coupling coefficient of the coupler attached to the passive ring resonator, _L2 is half the optical length of the passive ring resonator, ω is the angular frequency, c is the speed of light in vacuum, and _T0 is a constant.

Substitute (2)(3) into (1) to get:

$\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="0"\; label="T"\; filenames="HSA00000175780600022.png,HSA00000175780600031.png"\; state="\{\{state\}\}">T</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\underset{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; \&infin;</span>}{\overset{<span\; class="notranslate">\; +</span><span\; class="notranslate">\; \&infin;</span>}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>{<span\; class="notranslate">\; |</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; C</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="0"\; label="k"\; filenames="HSA00000175780600022.png,HSA00000175780600031.png"\; state="\{\{state\}\}">k</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&Delta;\; L</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;\&Delta;k</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&Delta;L</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="L"\; filenames="HSA00000175780600032.png,HSA00000175780600041.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}}<span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

Where L ₁ is the optical length of the active resonant cavity, ΔL=L ₂ −L ₁ , Δk=kk ₀ . In the general active resonant cavity 1 emission spectrum range, if the sensing range does not change much, there can be ΔL<<L ₁ and Δk<<k ₀ , so the high-order small amount in the denominator of (4) can be ignored 2πΔk(ΔL)/L ₁ , formula (4) can be transformed into:

$\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; =</span>{<span\; class="notranslate">\; |</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; C</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="0"\; label="k"\; filenames="HSA00000175780600022.png,HSA00000175780600031.png"\; state="\{\{state\}\}">k</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&Delta;L</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="L"\; filenames="HSA00000175780600032.png,HSA00000175780600041.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}}<span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

表示有源法布里-珀罗谐振腔发出的总功率。由式(5)可以看出，光功率探测器接收到的功率P与有源法布里-珀罗谐振腔和无源环形谐振腔的光程差异ΔL有关，当ΔL为0时，光功率探测器接收到的功率最大，两光程偏离越多，则接收到的功率越小。因此，当传感区21的光学长度受到外界环境因素诸如应力，温度或者被测物质浓度等改变时，无源环形谐振腔总光学长度就会发生变化，导致ΔL变化，从而引起光功率探测器接收到的光功率变化。通过测量该功率变化，就可以获得应力，温度等被测信息。in

Indicates the total power emitted by the active Fabry-Perot resonator. It can be seen from formula (5) that the power P received by the optical power detector is related to the optical path difference ΔL between the active Fabry-Perot resonator and the passive ring resonator. When ΔL is 0, the optical power The power received by the detector is the largest, and the more the two optical paths deviate, the smaller the received power will be. Therefore, when the optical length of the sensing region 21 is changed by external environmental factors such as stress, temperature or the concentration of the substance to be measured, the total optical length of the passive ring resonant cavity will change, resulting in a change in ΔL, thereby causing the optical power detector The received optical power varies. By measuring the power change, measured information such as stress and temperature can be obtained.

Figure 3 shows the fluorescence emission spectrum of an active Fabry-Perot resonator with a length of 200 μm, a refractive index of 3.215, and an operating wavelength of 1550 nm below the threshold current, as well as a length and refractive index related to the active resonator Cavity comparable, transmission spectrum of a passive ring resonator with a circumference of 400 μm. At this time, the optical path difference ΔL of the two resonators is 0, the fluorescence emission spectrum of the active resonator is aligned with the peak value of the transmission spectrum of the passive resonator, and the power emitted by the active resonator is 4.823mW. Figure 4 is the result of superposition of the fluorescence emission spectrum of the active Fabry-Perot resonator and the transmission spectrum of the passive ring resonator, that is, the output power spectrum of the entire sensor, and the total output power detected by the optical power detector is calculated is 3.995mW.

When the refractive index of the passive resonant cavity changes from 3.215 to 3.217 due to the influence of the external environment, the fluorescence emission spectrum of the active resonant cavity and the transmission spectrum of the passive resonant cavity are shown in Figure 5. At this time, due to the equivalent With the change of the refractive index, there is a small difference in the optical path of the two cavities. The peaks of the fluorescence emission spectrum of the active resonant cavity and the transmission spectrum of the passive resonant cavity are staggered from each other, and the power emitted by the active resonant cavity is still 4.823mW. Fig. 6 is the superposition result of the fluorescence emission spectrum of the active Fabry-Perot resonator and the transmission spectrum of the passive ring resonator, and the calculated total output power detected by the optical power detector is 0.2862mW.

Fig. 7 is a curve of the output optical power changing with the refractive index of the passive ring resonant cavity. It can be seen that a small change in the refractive index can cause a change in the output optical power of the sensor. In the range of 0～4×10 ^-4 of refractive index change, the power change is basically linear, and we can use this area for sensing.

It can be seen from the above examples that when the active resonant cavity works below the threshold, changes in external stress and temperature can be obtained by detecting changes in the output power of the sensor. Similar detection effects can also be obtained when the active resonant cavity works above the threshold.

Fig. 8 is the second embodiment of the optical sensor based on the active resonant cavity and the passive resonant cavity cascaded with it according to the present invention, which includes a comb-shaped spontaneous emission spectrum or laser spectrum with internal gain that can emit equal intervals The active ring resonator 5, the passive ring resonator 2 with equidistant comb filter spectrum, and an optical power detector 3, the active ring resonator is connected with the passive ring resonator through the third passive waveguide 51. In addition, the active ring resonator can also be a multi-segment active resonator with a distributed feedback grating structure inside, etc., which outputs equally spaced comb-shaped spontaneous emission spectrum or laser spectrum.

Fig. 9 is the third embodiment of the optical sensor based on the active resonant cavity and the passive resonant cavity cascaded with it of the present invention, which includes a comb-shaped spontaneous emission spectrum or laser spectrum with internal gain that can emit equal intervals Active Fabry-Perot resonator 1 and passive Fabry-Perot resonator 4 with equally spaced comb filter spectrum, and an optical power detector 3, passive Fabry-Perot resonator Including: the first mirror 42 of the passive Fabry-Perot resonator, the second mirror 43 of the passive Fabry-Perot resonator, the passive waveguide region 40 of the passive Fabry-Perot resonator, The passive Fabry-Perot resonant cavity sensing area 41 whose optical length can change with the external environment. In addition, the passive Fabry-Perot resonator can also be a multi-segment active resonator with a distributed feedback grating structure inside, which outputs an equally spaced comb-shaped spontaneous emission spectrum or a laser spectrum.

Fig. 10 is the fourth embodiment of the optical sensor based on the active resonant cavity and the passive resonant cavity cascaded with it of the present invention, which includes an active Fab with internal gain with equally spaced comb spectral output Re-Perot resonator 1 and a passive ring resonator 2 with equally spaced comb filter spectrum, and an optical power detector 3; the active ring resonator is an active ring resonator that applies a period and photons in the active resonator An active Fabry-Perot resonator 1 whose operating cycle is the same as the microwave driving signal 11 so as to keep its emission spectrum free from external interference.

It can be seen from formula (5) that the optical power obtained by the optical power detector 3 is related to the optical path difference between the active Fabry-Perot resonator 1 and the passive ring resonator 2, so any active Fabry-Perot resonator The change of the optical path of the resonator 1 will also cause power fluctuations, especially for multimode lasers working above the threshold, the output spectrum and power are unstable due to mode competition, which will interfere with the measurement results. However, if the aforementioned microwave signal 11 By driving the active Fabry-Perot resonant cavity 1, its resonant frequency can be precisely locked, thereby reducing the interference caused by the active Fabry-Perot resonant cavity 1 to the detection results and improving the sensitivity of sensing.

Fig. 11 is the fifth embodiment of the optical sensor based on the active resonant cavity and the passive resonant cavity cascaded with it of the present invention, which includes an active Fab with internal gain with equally spaced comb spectral output Re-Perot resonator 1 and a passive ring resonator 2 with equally spaced comb filter spectrum, and an optical power detector 3; in addition, in the active Fabry-Perot resonator second mirror 12 Another optical power detector 6 is arranged on the outer side of the , for receiving the output spectrum that has not been filtered by the passive ring resonator.

The output power of the active Fabry-Perot resonator 1 will fluctuate when it is disturbed by changes in the external environment, especially the output spectrum and power instability of the multimode laser working above the threshold due to the mode competition effect will affect the measurement As a result, there is interference, and the optical power obtained by the optical power detector 6 in this embodiment can reflect such power fluctuations. Therefore, by comparing the power obtained by the optical power detector 3 and 6, the external interference band can be filtered out. The power of the active resonant cavity is unstable, and the sensing accuracy is improved.

FIG. 12 is the sixth implementation of the optical sensor based on the active resonant cavity and the passive resonant cavity cascaded with it according to the present invention. It includes at least one active Fabry-Perot resonator 1 with an equally spaced comb spectral output with internal gain and a passive ring resonator 2 with an equally spaced comb filter spectrum, and a spectrometer 7; The optical lengths of the source Fabry-Perot resonator and the passive ring resonator are different, and at least a section of the passive ring resonator sensing region 21 whose optical length can change with the external environment is provided in the passive ring resonator, The spectrum emitted by the active Fabry-Perot resonator is input to the passive ring resonator through the first passive waveguide 22, and after being filtered by the passive ring resonator, it is received by the spectrometer 7 through the second passive waveguide 23 .

The optical path of the passive ring resonator in this embodiment is slightly different from that of the active Fabry-Perot resonator, and the resonant mode frequency intervals of the two resonators are also slightly different, which are Δf and Δf respectively, which makes the laser The resonant modes of the two resonators within the material gain spectrum completely coincide only at fo, as shown in Figure 13. At this time, only the light of frequency fo can pass through the passive ring resonant cavity with low loss, so the intensity of fo can be seen on the spectrometer is much greater than that of the adjacent modes. When the optical path of the passive ring resonator changes due to the change of the equivalent refractive index of the sensing region (the part inside the dotted line frame), the filtering spectral lines of the passive ring resonator will have an overall shift, resulting in the coincidence peaks towards the phase The adjacent harmonic peaks move, and the least common multiple of Δf and Δf becomes the free spectral range. The change of the relative optical power distribution of each resonance peak can be measured by using an external spectrometer 7 to measure the change of the refractive index. Due to the use of the vernier effect, this method has higher sensitivity than conventional single passive resonant rings.

Figure 14 shows the fluorescence emission spectrum of an active Fabry-Perot resonator with a length of 200 μm, a refractive index of 3.215, and a working wavelength of 1550 nm below the threshold current, and a circumference of 360 μm, with a refractive index corresponding to the Transmission spectrum of the same passive ring resonator as the active resonator. At this time, the resonant modes of the two resonators completely overlap at 1550nm, and in the emission spectrum of the active Fabry-Perot resonator, only the light energy with a wavelength of 1550nm passes through the passive ring resonator with low loss, and the light from the spectrometer The spectrum shown in Figure 15 can be obtained.

When the refractive index of the passive resonator changes from 3.215 to 3.2155 due to the influence of the external environment, the fluorescence emission spectrum of the active resonator and the transmission spectrum of the passive resonator are shown in Figure 16. Since the transmission spectrum of the passive ring resonator The resonant modes of the two resonators become completely overlapped at 1548nm, and only the light with a wavelength of 1548nm passes through the passive ring resonator with low loss, and the spectrum shown in Figure 17 is obtained on the spectrometer.

From the above analysis, it can be obtained that when the refractive index of the passive ring resonator changes by 5×10 ^-4 , the mode with the highest energy in the output spectrum of the sensor undergoes a jump, which can be simply calculated by the number of mode jumps The amount of change in the refractive index of the passive ring resonator waveguide is converted, and further transformed into changes in the external environment (such as temperature and humidity). In addition, when the refractive index changes between two states, we can further refine the resolution of the refractive index by outputting the power ratio between two energy-equivalent modes in the spectrum (as shown in Figure 18).

The above-mentioned embodiments are used to illustrate the present invention, but not to limit the present invention. Within the spirit of the present invention and the protection scope of the claims, any modification and change made to the present invention will fall into the protection scope of the present invention. For example, the active Fabry-Perot resonator can be replaced by any other active resonator that emits equally spaced comb-like spontaneous emission spectrum or laser spectrum, and the passive ring resonator can be replaced by any other that can generate periodic filtering Optical structures of spectral lines, such as etched diffraction gratings, arrayed waveguide gratings, sampled Bragg gratings, etc.

Claims (7)

1. An optical sensor based on an active resonant cavity and a passive resonant cavity cascaded therewith, characterized in that: comprising an active resonant cavity with an internal gain that can emit equally spaced comb-shaped spontaneous emission spectrum or laser spectrum and a passive resonant cavity with equidistant comb filter spectrum, and an optical power detector (3); the optical length of the active resonant cavity is the same as that of the passive resonant cavity, and at least one section of optical length can be arranged in the passive resonant cavity The passive resonant cavity sensing area that changes with the external environment, the spectrum emitted by an output port of the active resonant cavity is input to the passive resonant cavity, filtered by the passive resonant cavity, and then filtered by an optical power detector (3 ) received. 2. The optical sensor based on an active resonator and a passive resonator cascaded therewith according to claim 1, wherein the active resonator is an active Fabry-Perot resonator A cavity (1), an active ring resonant cavity (5) or a multi-segment active resonant cavity with a distributed feedback grating structure inside. 3. a kind of optical sensor based on active resonator and the passive resonator cascaded with it according to claim 1, is characterized in that: described passive resonator is passive ring resonator (2), A passive Fabry-Perot resonator (4) or a multi-segment passive resonator with a distributed feedback grating structure inside. 4. A kind of optical sensor based on an active resonant cavity and a passive resonant cavity cascaded with it according to claim 1, characterized in that: the active resonant cavity is an active A microwave driving signal (11) with the same operating period in the resonant cavity keeps its emission spectrum free from external interference. 5. The optical sensor based on an active resonant cavity and a passive resonant cavity cascaded with it according to claim 1, wherein another output port of the active resonant cavity is provided with another Optical power detector (6). 6. An optical sensor based on an active resonant cavity and a passive resonant cavity cascaded therewith, characterized in that: it includes an active resonant cavity that can emit equally spaced comb-shaped spontaneous emission spectrum or laser spectrum with internal gain And have the passive resonator of equidistant comb filter spectrum, and spectrometer (7); Described active resonator is Fabry-Perot resonator, and described passive resonator is passive ring resonator , the optical lengths of the Fabry-Perot resonator and the passive ring resonator are different, and the frequency intervals of the resonant modes of the two resonators are also different, so the resonant modes of the two resonators in the gain spectrum of the laser material are only at f ₀ The frequency of the passive ring resonator is completely coincident, and at least a passive ring resonator sensing area whose optical length can change with the external environment is provided in the passive ring resonator. When the optical path of the passive ring resonator is due to the equivalent refraction of the sensing area When the rate changes, the filter spectral line of the passive ring resonator will have an overall shift, causing the coincident peaks of the two resonators to move to the adjacent resonant peaks, and one output port of the Fabry-Perot resonator emits The spectrum is input to the passive ring resonator, and is received by the spectrometer (7) after being filtered by the passive ring resonator. 7. A kind of optical sensor based on an active resonant cavity and a passive resonant cavity cascaded with it according to claim 6, characterized in that: the active resonant cavity is an active A microwave driving signal (11) with the same operating period in the resonant cavity keeps its emission spectrum free from external interference.

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