RU2720063C1 - Spectrometer based on tunable laser on chip, and spectrum measuring method - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: spectrometer based on a tunable laser on a chip, comprises a laser radiation source for irradiating biological tissue with laser radiation, a photodetector for receiving radiation reflected from the biological tissue, having passed through the optical system, and a control and processing unit for signals received from the photodetector. Laser radiation source used is a tunable laser on a chip comprising a semiconductor amplifier and connected through an optical splitter to two or more resonators (A, B, ..., N) connected to a control and signal processing unit, wherein the semiconductor amplifier has its amplification band for operation of the tunable laser on the chip in a given wavelength range. Each of the resonators has a waveguide and tunable filters (A1, A2, B1, B2, ..., N1, N2), which provides generation of light at its output at different wavelengths (λ1, λ2, ..., λn), in accordance with parameters of tunable filters of each of resonators, wherein one of resonators A is intended for coarse high-speed measurement of the reflection spectrum R (λ) of the target when exposed to light generated by the adjustable filters A1 and A2 of the resonator, and the other of the resonators B is intended for accurate measurement of the reflection spectrum R (λ) of the target when exposed to light generated by the adjustable filters B1 and B2 of the resonator.

EFFECT: disclosed is a spectrometer based on a tunable laser on a chip.

12 cl, 12 dwg

Description

Technical field

The present invention relates to measuring technique, and more specifically to a spectrometer based on a tunable chip laser, and to a method for measuring a spectrum.

State of the art

Optical devices intended for use in spectroscopic purposes should have the characteristic of sweeping light wavelengths. This function can be realized using narrow-band tunable light sources, such as lasers, or using wide-band light sources, such as light emitting diodes (LEDs), in combination with an optical filter system. Both of these options suggest a cumbersome overall design of the light source system, which leads to an increase in the size of the entire spectrometer, which is difficult to fit into a wearable form factor. Form factor (from the English form factor) or size - a standard that defines the overall dimensions of a technical product, as well as describing additional sets of its technical parameters, for example, shape.

Currently There are three problems.

The first is the insufficient compactness of the spectrometer. A known spectrometer cannot be mounted on a hand in the form of a bracelet. In existing devices designed for this purpose, such compactness is not.

The spectral resolution of commercially available spectroscopic devices intended for use in a portable form factor does not exceed ~ 20 nm. However, non-invasive determination of blood glucose levels requires spectroscopic devices with a higher spectral resolution, which should be much less than a few nanometers.

The second problem is the low spectral resolution of known spectrometers.

When determining the glucose level, it is required to measure the reflection spectrum from the object, this can be realized either as a set of narrow-band light sources, such as a laser, or using a wide-band light source, such as light-emitting diodes, combined by an optical filter system, which implies a fairly large-scale design .

If the spectrum is measured using a set of narrow-band sources, then a set of points is obtained on this spectrum, the distance between which determines the resolution of the device. For existing devices, the resolution is not high enough, which does not meet the requirements of measuring such a parameter as blood glucose.

The third problem is the discreteness of wavelength tuning. In existing devices with tunable wavelength, such a rebuild is carried out discretely, i.e. in each time period, the tuning is performed to some fixed step, and the wavelength tuning, which is carried out continuously and smoothly, is not provided.

For scanning along the wavelength in existing optical spectroscopic devices, broadband LED sources are used in combination with individual optical filters or a set of narrow-band lasers. These elements are turned on and off in a predetermined sequence necessary for measurements. Such devices do not allow to obtain a continuous scan along the wavelength, which is important to achieve maximum measurement accuracy.

From the publication WO 2010/082852 (published July 22, 2010), a LED-based code source spectrometer is known which comprises a plurality of LED light sources that are capable of generating different wavelengths and bandwidths, said light sources being arranged in any convenient manner around the detector module, wherein The optical paths of the sample and the reference optical paths are different from each other. In preferred embodiments, the LED sources are switched in an encoded pattern or patterns corresponding to a Hadamard complement scheme or a modified Hadamard complement scheme.

The disadvantages of this spectrometer include sweeping of discrete wavelengths and low spectral resolution.

The spectrometer uses a large number of light emitting diodes and the spectral resolution is determined by the number of these diodes. If you want to increase the spectral resolution, you need to increase the number of light sources, i.e. number of diodes. But infinity cannot be increased, since the device is limited in size.

A non-invasive glucose sensor is also known (see, for example, US 7251516, published July 31, 2007). The glucose concentration is non-invasively measured by measuring the plurality of absorption values using at least one emitter operating at the corresponding plurality of radiation wavelengths through the total optical volume of the sample, and obtaining the glucose concentration from the absorption measurement values.

The non-invasive glucose sensor is configured, for example, in the form of a ball attached to a bracelet that people with diabetes can wear for continuous and non-invasive measurements of blood glucose. The sensor allows you to measure glucose, water and albumin non-invasively and continuously. The sensor can be implemented as a device of low power, small size and have a low cost. VCSEL Surface-Emitting Laser (VCSEL) is a type of semiconductor laser that can be configured as a tunable emitter. As a rule, semiconductor lasers with edge radiation have lower accuracy and are cheaper than (VCSEL).

In this device, so-called “vixels” are used as a light source — light-emitting sources with a vertical resonator, i.e. vertical cavity lasers emitting from a surface. This instrument does not imply wavelength tuning, several lasers are used here, and the number of these lasers determines the spectral resolution of the device. In addition, the use of a large number of these lasers is a rather expensive solution.

A tunable laser spectroscopic system is also known for non-invasive measurement of water content in the body (see, for example, US 2008/220512, published September 11, 2008). The water content in the body is one of the important indicators of health, with which you can quantitatively control the level of hydration of the body and determine whether it is necessary to add or reduce water in the body. The disclosed systems, devices and / or methods can improve the accuracy of the wavelength, resolution along the wavelength, the optical spectral power density, the signal-to-noise ratio and available implementations for the spectroscopy system.

The system comprises a laser configured and configured to illuminate at least a portion of body tissue, and one detector optically coupled to at least a portion of body tissue. For example, a system may include a tunable laser and / or one or more fixed wavelength lasers. The system in some embodiments, may include a sensor comprising a first optical fiber having a first end that is configured and configured to optically couple to a laser and having a second end that is configured and configured to optically communicate with a tissue sample; and a second optical fiber having a first end that is optically coupled to the detector, and a second end that is optically coupled to a tissue sample. The system may further include a wavelength division multiplexer and / or an optical switch in optical communication with the laser and the first optical fiber. A system, in accordance with some embodiments, may include a detector comprising a photodiode and / or an optical switch in optical communication with the second optical fiber. An optical fiber, for example, a first optical fiber and / or a second optical fiber, may comprise a coupler. The sensor is designed to be disposable or reused. The sensor may include a collimator, a star coupler and / or a beam expander optically coupled to the laser. In some embodiments, the system may exclude the grating and / or array of detectors.

The disadvantages of this device include the large size, which cannot be entered into the form factor.

As the closest technical solution, a spectrometer is considered (see, for example, US 2014/0168636, published June 19, 2014), comprising: a tungsten lamp (first light source) that emits light without a peak wavelength in the wavelength range of visible light, and the number light increasing with increasing wavelength; a purple LED (second light source) that emits light having a maximum wavelength (peak wavelength) in the wavelength range of visible light; a light mixer that mixes the light emitted by an incandescent lamp and a violet LED; a light receiving unit (reference) that receives light mixed by the light mixer and transmits light contained in the received mixed light and having a specific wavelength; a light receiving unit that receives light transmitted by the reference; and a measurement control unit that changes the wavelength of the light (i.e., characteristics of the test target light) that can pass through the standard, and measures the spectral characteristics of the light transmitted through the standard based on the light received by the light receiving unit.

When only the first light source is used that does not have a peak wavelength in the wavelength range of visible light, the amount of light within a certain range in the wavelength range of visible light is significantly reduced, as explained above. According to this aspect of the invention, a second light source that emits light having a peak wavelength, in particular in the short wavelength range (a wavelength range in which the amount of light from the first light source is reduced), can effectively compensate for the amount of light in the short wavelength range, where the amount of light from the first light source drops significantly. Accordingly, the accuracy of measuring spectral characteristics in the wavelength range where the amount of light decreases, can improve, which contributes to high-precision measurement of spectral characteristics.

The disadvantages of this spectrometer include sweeping of discrete wavelengths and low spectral resolution. Here, discrete wavelength tuning is performed. Smooth rebuilding is not carried out. There are certain steps that determine the resolution, and the rebuild is carried out with minimal sections, i.e. discretely.

Summary of the invention

An object of the present invention is to provide spectroscopic measurements with high spectral resolution and continuous wavelength tuning using means compact enough to fit the wearable form factor, while maintaining a low level of energy consumption, which is achieved by creating a spectrometer based on a tunable laser with the chip, which is compact so that it can be mounted on the arm in the form of a bracelet, has a high spectral resolution It provides rebuild wavelength, carried out continuously and smoothly.

The technical effect achieved by the claimed invention is to ensure compactness, i.e. satisfying the required form factor, higher measurement speed, high signal to noise ratio due to the use of lasers, and high spectral resolution and the ability to simultaneously perform coarse and accurate (if necessary) spectrum measurements.

The problem is solved by creating a spectrometer based on a tunable laser on a chip and containing

a laser radiation source configured to irradiate biological tissue with laser radiation,

a photodetector configured to receive radiation reflected from biological tissue that has passed through the optical system, and a control and processing unit for signals received from the photodetector,

in this case, a tunable chip laser containing a semiconductor amplifier and connected via an optical splitter with two or more resonators connected to a control and signal processing unit is used as a laser radiation source,

wherein the semiconductor amplifier has its own gain band for the operation of a tunable chip laser in a given wavelength range,

each of the resonators A, B ... N contains a waveguide and tunable filters (A1, A2, B1, B2 ... N1, N2), which ensures the generation of light at its output at different wavelengths (λ1, λ2, ..., λn), in accordance with the parameters of the adjustable filters of each of the resonators,

in this case, one of the resonators A is intended for coarse high-speed measurement of the reflection spectrum R (λ) of the target when it is irradiated with the light generated by the tunable filters A1 and A2 of this resonator, and the other of the resonators B is intended for accurate measurement of the reflection spectrum R (λ) of the target when it is irradiated with the light generated by the tunable filters B1 and B2 of this resonator.

Preferably, the waveguide of each of the resonators is terminated by a Sagnac mirror, which provides feedback between the resonator and the semiconductor amplifier.

Preferably, the spectrometer contains metal heating elements disposed in said one or more resonators and configured to supply voltage from an external source to them, and a thermo-optical control unit for metal heating elements configured to tune the resonator wavelength, wherein said wavelength rebuild is performed by applying voltage to the metal heating elements.

Preferably, the spectrometer contains

electro-optical control units by the number of resonators, configured to tune the wavelength of the resonators by applying an electric field to the resonators, a change in which causes a change in the effective refractive index of the resonators and, accordingly, a change in the transmission spectrum, which ensures the reconstruction of the wavelength.

Preferably, the spectrometer contains

acoustic-optical control units by the number of resonators configured to tune the wavelength of the resonators, while the wavelength is tuned by exposing the resonators to ultrasonic vibrations from an external source, and the parameters of the ultrasonic vibrations determine the transmittance spectrum, which ensures the tunable wavelength.

Preferably, the spectrometer contains an array of semiconductor amplifiers with different gain bands to provide sweep along a wavelength in an extended wavelength range.

Preferably, the spectrometer further comprises a modulation module configured to control the gain bandwidth of the semiconductor amplifier.

Preferably, the spectrometer comprises an additional feedback control unit and wavelength calibration units for calibrating the spectrometer wavelength in real time.

The problem is also solved by creating a method for measuring reflected radiation from a biological object by means of a spectrometer based on a tunable laser on a chip according to claim 1, containing steps in which

place the spectrometer on the patient’s arm and irradiate the biological tissue with laser radiation generated by two or more resonators, while one of the resonators A is designed for coarse high-speed measurement of the reflection spectrum R (λ) of the target when it is irradiated with the light generated by the adjustable filters A1 and A2, the other of the resonators B is designed for accurate low-speed measurement of the reflection spectrum R (λ) of the target when it is irradiated with the light generated by this resonator using custom filters B1 and B2,

carry out a coarse high-speed measurement of the reflection spectrum R (λ) of the target when it is irradiated with light generated by tunable filters A1 and A2 by one of the resonators A by tuning the wavelength of the source by changing the transmittance of tunable filters A1 and A2 of resonator A,

analyze the resulting spectrum of R (λ) and determine areas of interest to identify artifacts,

perform in the areas of interest accurate low-speed measurements of the reflection spectrum of the target when it is irradiated the light generated by tunable filters B1 and B2 of another resonator B.

It is preferable that in the method the wavelength of light in the waveguide is tuned by thermooptical tuning of the optical filters A and B along the wavelength, for which the waveguide is heated in the resonator, while the source wavelength changes from a smaller value to a larger one, and the filtering ability is determined by the refractive index the material from which the waveguides are made.

Preferably, in the method, the wavelength of the light in the waveguide is tuned by electro-optical tuning along the wavelength of the optical filters, for which the effective refractive index of the waveguide in the resonator is changed by applying an external electric field to the resonator waveguide, the source wavelength changing from a smaller value to more, and the filtering ability is determined by the refractive index of the material from which the waveguides are made.

It is preferable that in the method, the wavelength of the light in the waveguide is tuned by acousto-optic tuning of the optical filters along the wavelength, for which the transmission spectrum of the waveguide in the cavity is changed by applying ultrasonic vibrations to the specified waveguide, while the wavelength of the source changes from a smaller value to a larger one, moreover, the filtering ability is determined by the refractive index of the material from which the waveguides are made.

The proposed configuration of the spectrometer allows you to:

- simplify and miniaturize the entire optical circuit, where a semiconductor amplifier is the largest element;

- simultaneously and independently scan wavelengths λ1, λ2, etc., which provides greater flexibility in obtaining the spectrum of the biological tissue under study, sweeping is performed by changing the transmittance of tunable filters;

- use a smaller number of semiconductor amplifiers if several wavelengths are required, which reduces energy consumption and dispersion throughout the device;

- cover an extended range of wavelengths, for example, 1500-1800 nm, which is important for measuring blood glucose levels;

- to provide the possibility of implementing complex modulation of the output power, which is important for implementation in communication systems;

- provide higher accuracy of wavelength control due to real-time calibration.

Brief Description of the Drawings

The invention is further explained in the description of the preferred embodiments with reference to the accompanying drawings, in which:

FIG. 1 shows a general block diagram of a spectrometer;

FIG. 2 shows a general block diagram of a tunable chip laser containing a plurality of resonators;

FIG. 2A shows a general view of a semiconductor amplifier next to a coin,

FIG. 3 is a detailed diagram of a tunable chip laser containing two resonators;

FIG. 4 depicts a block diagram of a tunable chip laser;

FIG. 5 shows a radiation spectrum of a laser source of a spectrometer based on an array of tunable lasers;

FIG. 6 depicts a tunable laser circuit with thermo-optical resonator control units;

FIG. 7 depicts a tunable laser circuit with electro-optical / acousto-optical cavity control units;

FIG. 8 shows an array of tunable chip lasers made on a single substrate;

FIG. 9 is a diagram of a tunable laser comprising a real-time spectrometer wavelength calibration unit;

FIG. 10 shows a typical reflection spectrum of a sample obtained using a spectrometer with a laser source with an array of tunable chip-based lasers;

FIG. 11 depicts a typical reflection spectrum of a sample, measured roughly and at high speed;

FIG. 12 shows a typical reflection spectrum of a sample measured accurately and at a low speed in a selected region (B).

DESCRIPTION OF PREFERRED EMBODIMENTS

The spectrometer 1 (Fig. 1), based on a tunable chip laser, according to the invention, comprises a laser radiation source 2 configured to irradiate biological tissue 3 with laser radiation. The spectrometer 1 also contains a photodetector 4, configured to receive radiation 5 reflected from the biological tissue, transmitted through the optical system 6, which ensures the collimation of the radiation incident on it and directs it to the photodetector, and a control unit 7 for processing and processing signals received from the photodetector 4.

As a source of laser radiation 2, a tunable chip laser (Fig. 2) was used, which contains a semiconductor amplifier 8, combined with a photonic chip-substrate 9, and containing a set of resonators 10, and a cooling system 11.

In FIG. Figure 3 shows a detailed diagram of a tunable chip laser containing two resonators.

In FIG. 4 shows a block diagram of the indicated tunable chip laser using N resonators 10. A semiconductor amplifier 8, characterized by a certain amplification band of optical radiation, is connected using waveguides 12 (Fig. 3) through an optical splitter 13 with two or more resonators 10 (A, B ... N) associated with the control unit 18 and the power supply unit 19.

Each of the resonators 10 (A, B ... N), made on the basis of optical waveguides 12, contains tunable filters 14 (A, B, ... N), based on two cascade microresonators 16 (A and B), which ensures the generation of light on its output at different wavelengths (λ1, λ2, ... λn) (Fig. 4), in accordance with the parameters of these tunable filters 14 (A, B, ... N) in each of the resonators 10 (A, B, ... N) .

In a preferred embodiment of the spectrometer and laser source 2 (FIG. 3), two resonators 10 A and 10 B are used, in contrast to the general embodiment, involving the use of 2 or more resonators to some arbitrary number N (FIG. 4).

The tunable 14 A filter of the resonator 10 A is designed for coarse high-speed measurement of the reflection spectrum R (λ) of the target with the light generated in the resonator 10 A, while the tunable filter 14 V of the resonator 10 B is designed to accurately measure the reflection spectrum of R (λ) of the target when it is irradiated with light generated in the resonator 10 B.

The waveguide of each of the resonators 10 is terminated by a Sagnac mirror 15, which provides feedback between the resonator 10 and the semiconductor amplifier 8.

An optical splitter 13 divides the energy of one semiconductor amplifier 8 between two resonators 10. The main effect of this implementation is the simplicity of manufacture. Since these resonators are manufactured integrally, using SOI (silicon on insulator) technology, i.e. silicon on the insulator, or silicon nitride on the insulator using photolithography methods, the manufacture of this scheme on an industrial scale can be very simple.

The spectrometer 1 (Fig. 1) also contains metal heating elements 17 (Fig. 3) in the composition of the laser source 2, located on the surface of one or more tunable filters 14 as part of the resonators 10, and configured to supply voltage from an external source 19 ( Fig. 4).

The spectrometer 1 in a preferred embodiment comprises a thermo-optical control unit 17 for controlling metal heating elements (FIGS. 3, 6), which are configurable for tuning the wavelength of the resonators, wherein said tuning of the wavelength is performed by applying voltage to the metal heating elements.

In another embodiment, the spectrometer 1 contains electro-optical control units 20 (Fig. 7) by the number of resonators configured to tune the wavelength of the resonators by applying an electric field to the resonators, a change of which causes a change in the effective refractive index of the resonators and, accordingly, a change in the transmittance spectrum, which ensures a rebuild wavelengths.

In yet another embodiment, the spectrometer comprises acoustic-optical control units 20 (Fig. 7) by the number of resonators configured to tune the wavelength of the resonators, while the tune of the wavelength is performed by exposing the resonators to ultrasonic vibrations from an external source, the parameters of ultrasonic vibrations being determined transmittance spectrum that provides wavelength tuning.

An embodiment is possible when the spectrometer 1 contains an array of semiconductor amplifiers 8 (Fig. 8) with different amplification bandwidths, to ensure sweep along the wavelength in the extended wavelength range, for example, 1500-1800 nm.

As a rule, one semiconductor amplifier has its own gain band and the laser cannot work outside this band. This strip is limited. If it is necessary to measure the spectrum in a band that exceeds the gain band of the semiconductor amplifier, a different semiconductor amplifier with a different gain band should be used. By combining several tunable lasers, each of which is based on its own semiconductor amplifier with its own band, it is possible to simply combine their bands, i.e. dock one to the other to eventually cover the entire range.

An embodiment is possible when the spectrometer 1 further comprises a modulation module 21 (FIG. 9) configured to control the gain bandwidth of the semiconductor amplifier.

In yet another embodiment, spectrometer 1 comprises an additional feedback control unit 23 (FIG. 9) and wavelength calibration blocks 22 for calibrating the wavelength of spectrometer 1 in real time.

A method for measuring reflected radiation from a biological object by means of a spectrometer based on a tunable chip laser comprises the following steps.

Thanks to its compact size, the spectrometer can be placed on the patient’s arm. After placing the spectrometer, biological tissue is irradiated with laser radiation generated by two or more resonators 10 (Fig 3), while the tunable filter 14 A of the resonator 10 A is designed for coarse high-speed measurement of the reflection spectrum R (λ) (Fig. 10) of the target when it is irradiated with light generated by the resonator 10 A (Fig. 3).

A coarse high-speed measurement of the reflection spectrum R (λ) of the target is carried out when it is irradiated with the light generated in a custom filter 14 A of the specified one or more resonators by tuning the wavelength of the source by changing the transmittance of the custom filter 14 A of the resonator 10 (Fig. 3).

The resulting spectrum of R (λ) is analyzed (FIG. 11) and areas of interest are identified to identify artifacts. The region of interest, for example, may be a portion on the spectrum of the light source containing a sharp peak (Fig. 11, a rectangle shown by a dashed line).

Perform accurate low-speed measurements of the reflection spectrum of the target when it is irradiated in areas of interest the light generated by the resonator 10 B based on a tunable filter 14 B.

The rebuilding of the wavelength of light in the waveguide is carried out by thermo-optical rebuilding along the wavelength of the optical filter A and B, for which the waveguide is heated in the resonator, while the wavelength of the source changes from a smaller value to a larger one, and the filtering ability is determined by the refractive index of the material from which they are made waveguides.

It is also possible that the tuning of the wavelength of light in the waveguide is carried out by electro-optical tuning along the wavelength of the optical filter A and B, which involves changing the effective refractive index of the waveguide in the resonator by applying an external electric field to the resonator waveguide, while the wavelength of the source varies from smaller to larger, and the filtering ability is determined by the refractive index of the material from which the waveguides are made.

It is also possible that the reconstruction of the wavelength of light in the waveguide is carried out by acousto-optic reconstruction along the wavelength of the optical filter A and B, for which they change the transmission spectrum of the waveguide in the resonator by applying ultrasonic vibrations to the specified waveguide, while the wavelength of the source changes from a smaller value to a greater one, and the filtering ability is determined by the refractive index of the material from which the waveguides are made.

Smooth tuning along the wavelength is carried out using two microresonators 16 (Fig. 3), which are part of each of the tunable filters 14 A and 14 V, operating using the Vernier effect.

In this case, this effect is expressed in a significant increase in the range of resonator tuning due to the cascade arrangement of two microcavities 16A, 16B, which have different transmission spectra of optical radiation.

перестроения резонатора, состоящего из двух микрорезонаторов, определяется согласно выражению If the distance between the transmission peaks (and, accordingly, the range of tuning of the wavelength of the transmitted optical radiation) of the first microcavity is defined as FSR ₁ and the second as FSR _2, then the range

rebuilding a resonator consisting of two microresonators is determined according to the expression

,

,

which can significantly exceed the values of FSR ₁ and FSR _2.

As indicated above, if it is necessary to measure the spectrum in a band that exceeds the gain band of the semiconductor amplifier, another semiconductor amplifier with a different gain band is used. By combining several tunable lasers, each of which is based on its own semiconductor amplifier with its own band, it is possible to simply combine their bands, i.e. dock one to the other to eventually cover the entire range.

Figure 5 shows a certain reference spectrum based on an array of tunable lasers.

At some initial point in time, the emission spectrum is a set of narrow wavelength bands that cover the range from 1500 to 1800 nm. This range is determined by the object of study. If biological objects should be measured, for example, the glucose content in human tissues, it is necessary to measure the spectrum in this range, i.e. one semiconductor amplifier, which covers approximately 50 nm, this is impossible to achieve. You need to use several semiconductor amplifiers.

Figure 10 shows a demo version of the reflection spectrum from the object, which will turn out if measured using an array of tunable lasers. As a result, a curve is obtained on which each point corresponds to the reflection spectrum of its wavelength from the object.

The solid line shows the spectrum of the source, the dashed line shows the reflection spectrum of an object, for example, biological tissue. In this case, it is shown that it is possible to obtain a very rough spectrum, i.e. how many wavelengths, so many points they get - this is a broken curve. This may not be very informative at the initial stage, but it allows you to estimate the time and highlight areas that are important for more accurate measurement in the future.

It is noted below what function the resonator performs:

- the resonator provides feedback, i.e. part of the radiation passing through it is sent back for amplification;

- the resonator provides filtering of radiation.

Theoretically, any filter, optical or based on some other effect, can perform this function.

The claimed configuration of the spectrometer allows when radiation with two different wavelengths λ1 and λ2 is generated simultaneously, firstly, to significantly reduce the size of the entire circuit, because there is one biggest element - a semiconductor amplifier. And if using a single gain chip two different wavelengths are obtained at the output, then the circuit is halved compared to a circuit with two semiconductor amplifiers that would provide two different wavelengths. But the energy of a semiconductor amplifier cannot be divided forever.

And in addition, such a scheme makes it possible to implement the claimed method of measuring the spectrum by simultaneously tuning two different wavelengths using any given algorithm.

Thus, a selective measurement of the spectrum. Two spectrum measurement modes, i.e. rough and accurate measurements are directly related to the use of two wavelengths obtained from a single semiconductor amplifier. Since there are two radiation waves, it is possible to carry out a rough measurement for one wavelength, and an accurate measurement for the second wavelength.

This is provided as follows. At the initial moment, with the help of one filter, one resonator based on the Vernier effect, the wavelength tuning is provided when the wavelength of the source changes from shorter to greater with the maximum possible permissible speed. But the higher the speed, the lower the resolution, the lower the noise signal. In this case, a certain rough spectrum of reflection from the object is obtained. It is subject to fluctuations, it can be noisy, because the measurement was carried out very quickly. In this case, a relatively small amount of energy is detected at each moment in time.

After a rough measurement of the spectrum has been carried out, the resulting curve is analyzed and the areas that are most interesting and important on it are found.

As a rule, when measuring glucose, the spectrum itself is not entirely as informative as its individual parts. This is especially true in cases where the spectrum is used to determine some relative change in glucose or some chemical substance. Those. The definition of a relative spectrum measurement may be relevant. In this case, one should consider some parts of the spectrum and how they change.

These sections are then measured with higher accuracy. For this, the exact measurement mode using the second wavelength is used. Those. change the parameters of the second resonator in such a way that the wavelength tuning is carried out with a certain minimum speed, but not in the entire range, but in the range of interest.

Those. First, with a single filter, they quickly scan, determine the portion of the spectrum that is of interest, and within it scan slowly using the second wavelength.

The advantage of using two wavelengths is as follows. The filtering ability of optical filters is determined by the temperature dependence of the effective refractive index of the material from which they are made. Those. rebuilding is carried out by heating these resonators. Heating is an inertial process and heating special metal contacts is much easier than cooling, especially in a wearable device where special active cooling systems are not provided. In this case, due to the presence of two separate filter sets with two radiation sources, it is possible to provide heating of one resonator, coarse tuning, and then fine tuning, heating the second resonator, without the need to cool the first resonator, wait a while until it is sufficiently cooled, in order to carry out perestroika again with his help. In this case, the productivity and speed of the entire device is increased.

The main advantage is that, using two sources, it is not necessary to cool each of them, you can scan twice, the first and second, heating the first and second alternately.

In the second case, the reconstruction of microresonators can be achieved not only with a change in temperature, i.e. by heating, but also with the help of various electro-optical effects. Those. if not ordinary silicon is used to create microresonators, but various materials that have a significant electro-optical effect, i.e. by changing the effective refractive index depending on the external electromagnetic field applied to them, for example, lithium niobate refers to such materials, it is possible not to change the temperature, but to change the applied electromagnetic field.

In case the wavelength calibration unit 22 is used, the operation is as follows.

Each of the radiation sources generates light that enters the calibration unit 22. Calibration unit 22 determines whether the generated wavelength really corresponds to that laid down in the resonator 10 control algorithm. Tuning is carried out on the assumption that there is a certain relationship between the control signal and the wavelength of the resulting radiation.

However, this dependence is subject to external influence, some kind of interference. In the case of temperature, there may be some effects associated with additional heating of the entire substrate on which the circuit is placed. And the wavelength may differ from the desired, i.e. There is a difference between the true and the required wavelength. To compensate for this effect, an additional wavelength calibration module is used, which is combined with the feedback module of the power supply of the semiconductor amplifier.

Comparing the wavelength and receiving in this block a signal about the difference between the true and the required wavelength, a feedback signal is generated and the power of the semiconductor amplifier is changed to reduce the signal and change the required wavelength.

Industrial applicability

The proposed spectrometer can be used for: measuring the change in the concentration of glucose in the blood, measuring the level of blood oxygenation, i.e. saturation of blood with oxygen, determination of blood pressure, determination of subcutaneous fat, assessment of human skin condition for cosmetic purposes, assessment of skin moisture level, as well as food quality assessment, drug evaluation, analysis of drinking bottled water.

Claims (29)

1. A spectrometer based on a tunable chip laser, comprising: a laser radiation source configured to irradiate biological tissue with laser radiation, a photo detector configured to receive radiation reflected from biological tissue that has passed through the optical system, and control unit and processing signals received from the photodetector, in this case, a tunable chip laser containing a semiconductor amplifier and connected through an optical splitter with two or more resonators (A, B, ..., N) connected to a control and signal processing unit is used as a laser radiation source, wherein the semiconductor amplifier has its own gain band for the operation of a tunable chip laser in a given wavelength range, each resonator contains a waveguide and tunable filters (A1, A2, B1, B2, ..., N1, N2), which ensures the generation of light at its output at different wavelengths (λ1, λ2, ..., λn), in accordance with parameters of custom filters for each of the resonators, in this case, one of the resonators A is intended for coarse high-speed measurement of the reflection spectrum R (λ) of the target when it is irradiated with the light generated by the tunable filters A1 and A2 of this resonator, and the other of the resonators B is intended for accurate measurement of the reflection spectrum R (λ) of the target when it is irradiated with the light generated by the tunable filters B1 and B2 of this resonator. 2. The spectrometer according to claim 1, in which the waveguide of each of the resonators is terminated by a Sagnac mirror, which provides feedback between the resonator and the semiconductor amplifier. 3. The spectrometer according to claim 1, which contains metal heating elements located in the specified one or more resonators and configured to supply voltage to them from an external source, and thermo-optical control unit for metal heating elements configured to tune the wavelength of the resonators, while the specified wavelength tuning is performed by applying voltage to the metal heating elements. 4. The spectrometer according to claim 1, which contains electro-optical control units by the number of resonators, configured to tune the wavelength of the resonators by applying an electric field to the resonators, a change in which causes a change in the effective refractive index of the resonators and, accordingly, a change in the transmission spectrum, which ensures the reconstruction of the wavelength. 5. The spectrometer according to claim 1, which contains acoustic-optical control units by the number of resonators configured to tune the wavelength of the resonators, while the wavelength is tuned by exposing the resonators to ultrasonic vibrations from an external source, and the parameters of the ultrasonic vibrations determine the transmittance spectrum, which ensures the tunable wavelength. 6. The spectrometer according to claim 1, which contains an array of semiconductor amplifiers with different gain bands to provide sweep along the wavelength in the extended wavelength range. 7. The spectrometer according to claim 1, which further comprises a modulation module configured to control the gain bandwidth of the semiconductor amplifier. 8. The spectrometer according to claim 1, which contains an additional feedback control unit and wavelength calibration units for calibrating the spectrometer wavelength in real time. 9. A method of measuring reflected radiation from a biological object by means of a spectrometer based on a tunable laser on a chip according to claim 1, comprising the steps of place the spectrometer on the patient’s arm and irradiate the biological tissue with laser radiation generated by two or more resonators, while one of the resonators A is designed for coarse high-speed measurement of the reflection spectrum R (λ) of the target when it is irradiated with the light generated by the adjustable filters A1 and A2, the other of the resonators B is designed for accurate low-speed measurement of the reflection spectrum R (λ) of the target when it is irradiated with the light generated by this resonator using custom filters B1 and B2, carry out a coarse high-speed measurement of the reflection spectrum R (λ) of the target when it is irradiated with light generated by tunable filters A1 and A2 by one of the resonators A by tuning the wavelength of the source by changing the transmittance of tunable filters A1 and A2 of resonator A, analyze the resulting spectrum of R (λ) and determine areas of interest to identify artifacts, perform, in areas of interest, accurate low-speed measurements of the reflection spectrum of the target when it is irradiated with light generated by custom filters B1 and B2 of another resonator B. 10. The method according to p. 9, in which tuning the wavelength of light in the waveguide by thermooptical tuning along the wavelength of the optical filters, for which the waveguide is heated in the resonator, while the wavelength of the source changes from a smaller value to a larger one, and the filtering ability is determined by the refractive index of the material from which the waveguides are made. 11. The method according to p. 9, in which the light wavelength in the waveguide is rebuilt by electro-optical reconstruction of the optical filters along the wavelength, for which the effective refractive index of the waveguide in the resonator is changed by applying an external electric field to the resonator waveguide, while the source wavelength changes from a smaller value to a larger one, and the filtering ability determined by the refractive index of the material from which the waveguides are made. 12. The method according to claim 9, in which the reconstruction of the wavelength of light in the waveguide by acousto-optic reconstruction along the wavelength of the optical filters, for which they change the transmission spectrum of the waveguide in the cavity by ultrasonic vibrations on the specified waveguide, while the wavelength of the source varies from smaller to larger, and the filtering ability is determined by the refractive index of the material from which the waveguides are made.

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