KR20020008266A - Angle sensor using photonic quantum ring laser - Google Patents

Abstract

PURPOSE: An azimuth angle sensor by using PQR(Photonic Quantum Ring) laser is provided to conveniently produce the azimuth angle sensor by simplifying structure and to extend measuring range of the azimuth angle. CONSTITUTION: An azimuth angle sensor by PQR laser comprises a PQR laser changing output spectrum wave according to the azimuth angle; an optical spectrum analyzer measuring wave of the output spectrum of the PQR laser; and an angle changing algorithm; a first DBR formed on a semiconductor base plate; a cavity layer installed on the first DBR; a second DBR formed on the cavity layer; and a unit element containing the second DBR. The cavity layer and the second DBR are mesa structure by having a smaller diameter than the semiconductor case plate and the first DBR. The mesa structure of the cavity structure and the second DBR is formed by a CAIBE(Chemically Assisted Ion Beam Etching) method. Thereby, the azimuth angle sensor by the PQR laser extends a measuring range of the azimuth angle.

Description

Angle sensor using photonic quantum ring laser

The present invention relates to an azimuth sensor, and more particularly to an azimuth sensor using a laser.

Mobile robots, which are widely used in factory automation today, are mainly used in the form of automatic guided vehicles (AGVs) due to the limitation of the perception of the surrounding environment. The unmanned vehicle runs only a predetermined route in a place where logistics automation is required, such as a factory or a warehouse. Instead, the mobile robot itself needs to recognize the surrounding environment and calculate and drive the most efficient route to the desired destination.

This requires the development of a sensor with excellent perception of the environment. Ultrasonic sensors, which are general sensors for measuring medium distances, are widely used because of their simple connection method and low cost. However, due to the lack of environmental awareness of the sensor itself, it is difficult to expect good environmental awareness.

Cameras that are widely used these days have the advantage of acquiring images as can be seen by real people, but real time automation technology is difficult to realize due to the time delay caused by massive data processing.

On the other hand, a sensor using a laser can perform a function having both the advantages of an ultrasonic sensor and a camera, and existing laser technology is limited to the conventional technology of distance measurement using a Doppler effect. On the other hand, the angle sensing technique is usually tied to a primitive level using an encoder technique that optically reads the scales of the mechanical rotation angle of the rotating shaft, and can be mixed and used separately from the distance measuring technique.

Therefore, there is a need for the development of a sensor that can give a mobile robot superior environmental awareness than an ultrasonic sensor or camera.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide an azimuth sensor having a wide range of measurable azimuth angles and a wide range of measurement distances to impart excellent environmental awareness to a mobile robot. have.

1 is a cross-sectional view of a photon frame laser unit device used in the azimuth sensor according to the present invention.

2A and 2B are close-up photographs of an 8 × 8 photon frame laser array used in an azimuth sensor according to the present invention under transparent and threshold conditions, respectively.

3 is a result of measuring the spectrum according to the distance of the 8 × 8 photon frame laser array used in the azimuth sensor according to the present invention.

4 is a result of measuring the spectrum of the 8 × 8 photon frame laser array used in the azimuth sensor according to the present invention according to the distance change in the horizontal direction (x-axis) and the measurement distance at a constant measurement distance.

5 illustrates an interference effect calculated by modeling an 8 × 8 point light source having the same shape as an 8 × 8 photon frame laser array device used in an azimuth sensor according to the present invention.

6 is a result of measuring the spectrum according to the azimuth angle of the photon frame laser unit device used in the azimuth sensor according to the present invention.

7 is a result of measuring the spectrum according to the azimuth angle at a distance of 80 cm for the 8 × 8 photon frame laser array used in the azimuth sensor according to the present invention.

8 shows the light emitted from the photon frame laser element.

9 is a result of measuring the spectrum according to the azimuth angle of the device well controlled around the mesa.

In order to achieve the object as described above, the azimuth sensor using a photonic quantum ring (PQR) laser according to the present invention, the photon laser having a wavelength of the output spectrum changes according to the azimuth angle; And an optical spectrum analyzer and an angle conversion algorithm for measuring the wavelength of the output spectrum of the photon laser.

At this time, the photon laser is an array structure consisting of a unit device including a semiconductor substrate, a first DBR formed on the semiconductor substrate, a cavity layer formed on the first DBR, and a second DBR formed on the cavity layer, and unit The device is characterized in that the cavity layer and the second DBR are mesa structures formed so as to have a diameter smaller than that of the semiconductor substrate and the first DBR.

In addition, in the mesa structure, the side surfaces of the cavity layer and the second DBR are etched using a chemically assisted ion beam etching (CAIBE) method.

Hereinafter, an azimuth sensor using a photon frame laser array according to the present invention will be described in detail with reference to the accompanying drawings.

In general, a laser is injected with an electric current to generate light in an active layer, and the light is amplified by the reflection of the mirror surface, and the light is amplified sufficiently beyond a certain limit (called threshold current). It comes through the surface.

The vertical cavity surface emitting laser (VCSEL, VCSEL) device, which is currently being researched, has a density of 8 × 8 when an array of a plurality of unit devices is manufactured. It stays at a low level because the VCSEL array requires relatively high drive current. At high drive currents above mA, it is not possible to fabricate a uniform, highly integrated VCSEL array due to heat irregularities in the array plane. (IEEE J. Selected topics in Quant. Elec., Vol. 1, pp. 681-696, 1995)

On the other hand, the photon frame laser used in the azimuth sensor according to the present invention can be operated from a class-class microcurrent, and the photon frame can be operated even at actual temperature above room temperature due to the characteristic that the spectrum approximates the saturation point in proportion to the square root of temperature. There is a big advantage that the oscillation wavelength of the laser is stabilized. Therefore, when fabricating a photon frame laser device in an array, high integration is possible compared to a VCSEL array.

1 is a cross-sectional view of a photon frame laser unit device used in an azimuth sensor according to the present invention, in which the epitaxial structure of the photon frame laser device is shown. The epitaxial structure shown in FIG. 1 is grown by metal organic vapor phase epitaxy (MOVPE), and the n-GaAs buffer layer and about 40 layers of n-DBR (n-GaS) on the n + GaAs substrate 1 2) are formed in order, 1-λ cavity layer (4) having four quantum wells on the n-DBR (2) and a spacer layer (3) at the top and bottom, p-DBR (about 30 layers) 5) and an upper layer formed of p + GaAs 6 for negative contact, in turn, to have a narrower diameter than the lower layer consisting of an n + GaAs substrate 1, an n-GaAs buffer layer, and an n-DBR (2) Mesa structure.

As described above, the method for producing an epitaxial structure of a photon-type laser device, first, the n-GaAs buffer layer, n-DBR (2), on the n + GaAs substrate (1) by the metal organic chemical vapor deposition described above After forming the 1-λ cavity (4), the p-DBR (5), and the p + GaAs layer (6) in sequence, the upper layer 1-λ cavity (4) using a chemically assisted ion beam etching method to form a mesa structure , p-DBR (5), and p + GaAs (6) layers are etched to form a narrower diameter than the underlying layer made of n + GaAs substrate 1, n-GaAs buffer layer and n-DBR (2). At this time, the researchers of the present invention were able to control the unevenness of the side surface of the upper layer by a chemically assisted ion beam etching method using the newly manufactured equipment.

Next, sulfides are formed to prevent the formation of an oxide film on the surface etched by the chemical auxiliary ion beam etching method.

Next, in order to insulate the devices and planarize the devices, a polyimide is filled in the upper part of the device, including a distance between the devices due to the mesa structure, and then polished and planarized.

A close-up photograph of an epitaxial photon laser device manufactured by the method as described above is shown in FIGS. 2A and 2B.

In the photon frame laser according to the present invention, the light waves formed in the active layer are propagated in the donut-shaped region in both directions, and when the two directions meet at some point, the light waves satisfy the fabry-perot resonance condition.

2A and 2B, the photon frame laser unit device has a diameter of 15 μm, and a space between unit devices is 35 μm.

FIG. 2A shows a state in a transparent condition, where the current is 0.1 mA for the entire 8x8 array, that is, 1.56 mA per unit element. FIG. 2B shows a state of a threshold condition, where the threshold current is 1 mA for the entire 8x8 array, that is, 15.6 mA per unit device. As shown in Figure 2a and 2b, it can be seen that the characteristics of the photon frame laser unit device used in the present invention is similar to the conventional unit device.

Figure 3 shows the results of measuring the spectrum according to the distance of the 8 × 8 photon frame laser array as described above, the distance from the photon frame laser array is 5 cm, 10 cm, 20 cm, 30 cm, 40 cm The output spectrum is measured for each case, 50 cm, 60 cm, 70 cm and 80 cm.

At this time, the photon laser array was driven in continuous wave (CW) mode, the injection current was 200 mA, 3.125 mA per unit device, and the oscillation wavelength was 780 nm.

As shown in FIG. 3, spectrum analysis was possible even at a distance of 80 cm, whereas in case of a unit device having a mesa size of the same diameter, spectrum analysis is possible only within a distance of about 3-4 mm. Arrays of 8x8 can be used to analyze spectra at distances of several tens of centimeters or more.

From this, it can be seen that the measurement range can be extended to several tens of meters by using more integrated arrays or by connecting multiple 8 × 8 arrays in parallel.

In FIG. 3, the greater the intensity of the spectrum at a distance of 40 cm and 60 cm than at a distance of 30 cm and 50 cm, respectively, indicates that the light emitted from each array causes an interference effect and thus some degree of periodicity. This is because there is a maximum and minimum position to

In order to measure the interference effect in more detail, it was investigated how far the intensity change of the wavelength was in the unit plane by moving the photon laser device at a constant measurement distance in the horizontal direction (x axis) little by little. The results are shown in FIG.

As shown in Fig. 4, the maximum and minimum positions having a predetermined periodicity appear due to the interference effect.

FIG. 5 illustrates an interference effect calculated from a point light source at a distance of 30 cm by modeling an 8 × 8 point light source having the same shape as the photon frame laser array device of the present invention.

The photon frame laser array device as described above has a multi-wavelength characteristic in which the center wavelength of the spectrum is shifted according to the azimuth angle, and this multi-wavelength characteristic is used for the azimuth sensor.

FIG. 6 illustrates multi-wavelength characteristics according to azimuth angles of the photon-telemetry laser unit element, and the wavelength of the spectrum is 795 for each case where the azimuth angles are 0 °, 15 °, 30 °, 45 °, 60 °, and 75 °. By shifting to nm, 792 nm, 786 nm, 779 nm, 772 nm and 764 nm, multiwavelength characteristics on the order of about 30 nm are shown.

FIG. 7 shows the azimuth spectra of an 8 × 8 photon laser array measured at a distance of 80 cm, showing the measured spectra for each case with an azimuth angle of 0 °, 15 °, and 30 °, respectively. Azimuth-multi-wavelength characteristics similar to those of unit devices are shown.

7 shows that the spectrum is measured for an azimuth angle of up to 30 ° in one direction, and thus it is possible to measure up to 60 ° azimuth in a two-dimensional plane in consideration of bidirectional, that is, -30 °.

FIG. 8 illustrates light emitted from the photon-type laser element, and as shown therein, light waves travel in a spiral form inside the photon-type laser element, wherein forward and backward directions are different. At the point of meeting, the light meets the Fabry-perot resonance condition and light is emitted in the direction of the vector sum in two directions. As a result, multi-wavelength characteristics according to the azimuth angle as shown in FIGS. 6 and 7 can be obtained.

The modes output in this vector sum direction exist at different wavelengths, which can be seen from the spectral results in devices with well controlled mesa side roughness. FIG. 9 shows the spectra when the azimuth angles are 0 ° and 10 ° for the photon-element laser unit device in which the roughness of the side of the mesa is well controlled by the chemically assisted ion beam etching method. As shown here, the modes appearing in the vector sum direction exist at different wavelengths, and the wavelength of the output spectrum is changed by the coupling efficiency of the optical fiber which depends on the azimuth angle, which is the angle between the optical fiber for observing the output spectrum and the device. .

When using the multi-wavelength characteristics of the photon frame laser in the azimuth sensor, only a light spectrum analyzer and an angle conversion algorithm for detecting the wavelength of the laser by connecting the photon frame laser array to a computer, without the need for a separate complicated device, Measure the azimuth angle with.

As described above, the azimuth sensor using the photon frame laser device according to the present invention, an optical spectrum analyzer for detecting the wavelength of the laser by connecting the photon frame laser array and a computer without the need for a separate data processing or sensor device of a complex circuit And since the azimuth angle is measured only by the angle conversion algorithm, the structure and manufacturing method of the azimuth sensor has a very simple effect.

In addition, the photon frame laser used in the azimuth sensor according to the present invention can be operated from a small class current, and the oscillation wavelength of the photon frame laser is stable even at an actual temperature of room temperature or higher, so that it can be highly integrated when manufactured as an array. It is effective to extend the measuring distance of several tens of meters.

In addition, the azimuth sensor using the photon laser according to the present invention has an effect that can be measured up to an azimuth angle of about 60 ° in a two-dimensional plane.

Claims (3)

A photon frame laser whose wavelength of the output spectrum changes in accordance with the azimuth angle; An optical spectrum analyzer for measuring a wavelength of an output spectrum of the photon laser; Angle conversion algorithm Azimuth sensor using a photon frame laser including a. The method of claim 1, wherein the photon laser, An array structure including a unit substrate including a semiconductor substrate, a first DBR formed on the semiconductor substrate, a cavity layer formed on the first DBR, and a second DBR formed on the cavity layer, The unit device may have an mesa structure in which the cavity layer and the second DBR have a diameter smaller than that of the semiconductor substrate and the first DBR. The method of claim 2, wherein in the mesa structure, Side surfaces of the cavity layer and the second DBR are etched using a chemically assisted ion beam etching (CAIBE) method.