KR100701153B1 - Wavelength tunable light source - Google Patents

Abstract

A wavelength variable light source is provided to minimize optical coupling loss between two materials and to increase reliability by easily hybrid-integrating a diffraction grating made from silicon or polymer except for a diffraction grating made from indium phosphide. A wavelength tunable light source(700) is composed of an optical amplifier(710) transmitting an optical signal having a predetermined wavelength band in one direction and amplifying and outputting an optical signal having a predetermined single wavelength of the wavelength band in another direction; a beam steering unit(720) for moving an output path of the optical signal having a predetermined wavelength band; and a waveguide of which one end is formed in a linear structure connected with the beam steering unit to flatly spread and transmit the optical signal having the wavelength band and the other end is formed like a concave diffraction grating(730) generating constructive interference of a single wavelength at one end by reflecting and diffracting the optical signal having the wavelength band. The constructively interfered single wavelength has a straight trajectory and feeds back to the optical amplifier through the beam steering unit.

Description

Wavelength Tunable Light Source

FIG. 1 is a view illustrating a structure of an external resonator type variable wavelength light source device having a litto form among conventional variable wavelength light source devices.

FIG. 2 is a view illustrating a structure of an external resonator type variable wavelength light source device of a Litman type among conventional variable wavelength light source devices.

3 is a diagram illustrating a structure of a deflector integrated wavelength variable light source device including a Roland circle diffraction grating.

4 is a structural diagram for explaining a variable characteristic of the wavelength tunable laser of FIG.

FIG. 5 is a diagram illustrating the structure of a beam steer integrated wavelength variable light source element including a Roland circle diffraction grating.

FIG. 6 is a structural diagram illustrating a variable characteristic of the wavelength tunable laser of FIG. 5.

7 is a diagram illustrating a structure of a beam adjuster integrated wavelength variable light source device including a diffraction grating such that the trajectory of the variable wavelength beam according to the present invention is a straight line.

8 is a view for explaining the principle of the diffraction grating structure such that the trajectory of the variable wavelength beam according to the present invention of FIG.

9 is a wavelength variable of a structure in which a diffraction grating is made of silicon or polymer so that the trajectory of the variable wavelength beam according to the present invention of FIG. It is a figure which shows the structure of a light source element.

10 is a diagram illustrating a structure of a deflector integrated wavelength variable light source device including a diffraction grating such that the trajectory of the variable wavelength beam according to the present invention is a straight line.

FIG. 11 is a diagram illustrating a structure of a beam adjuster integrated wavelength variable light source device including a diffraction grating for satisfying the Rietman condition and allowing the path of the variable wavelength beam to be straight.

FIG. 12 is a view illustrating a structure of a wavelength tunable light source device having a diffraction grating made of silicon or polymer according to the present invention of FIG. 11 and having a single integrated material of an optical amplifier and a beam manipulator, an indium phosphorus and a hybrid integrated structure.

FIG. 13 illustrates a structure of a deflector integrated wavelength variable light source device including a diffraction grating which satisfies the Ritman condition and makes the trajectory of the variable wavelength beam linear.

FIG. 14 is a flowchart illustrating an operating principle of the tunable light source device of FIG. 7.

15 is a flowchart illustrating an operating principle of the tunable light source device according to the present invention of FIG. 11.

 BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tunable light source device, and more particularly to an optical amplifier, a beam steering unit or a beam deflection unit, and a concave diffraction grating. The present invention relates to a wavelength tunable light source.

In general, the importance of the tunable semiconductor laser (wavelength variable light source device) is increased as the light transmission scheme such as wavelength division multiplexing is used. The tunable semiconductor laser can not only replace several wavelength fixed semiconductor lasers emitting different wavelengths, but also reconfigurable optical add / drop multiplexer (ROADM), fast packet switching in all optical networks. Packet switching, wavelength converters, wavelength routers, and the like are also actively utilized. In addition, the application range of the light meter and sensor, medical, measurement, etc. is very wide and diverse. Accordingly, the world's leading companies are introducing a wide variety of tunable semiconductor lasers. Herein, an external resonator-type wavelength tunable semiconductor laser among conventional tunable semiconductor lasers will be described in order to clearly compare the structure of the present invention.

FIG. 1 is a view illustrating a structure of an external resonator type variable wavelength light source device having a litto form among conventional variable wavelength light source devices.

Specifically, the external resonator type tunable light source device includes a semiconductor laser coated with an anti-reflection film 115 (laser diode LD), an external diffraction grating 120 and a lens 130. It consists of). The beam 140 may be generated by applying a current ILD to the semiconductor laser 110. When the beam 140 generated by the semiconductor laser 110 reaches the diffraction grating 120 via the lens 130, the beam 140 is returned to the following equation 1 with respect to the incident angle θ to the vertical line 100 of the diffraction grating plane. (Littrow) The wavelength of the beam 150 to be diffracted is determined according to the diffraction grating formula, and only the diffraction beam 150 having a specific wavelength is fed back to the semiconductor laser 110 to output light Pout.

Where m is the diffraction order, λ is the wavelength, d is the period of the diffraction grating, and θ is the angle of incidence.

When the diffraction grating 120 is moved with respect to a pivot point 105, which is a virtual point where the left end of the semiconductor laser 110 meets the plane of the diffraction grating 120, the diffraction grating 120 rotates 160. The incident angle θ is changed and the wavelength is changed by Equation (1).

If only the incident angle [theta] is changed, the wavelength tunable characteristic has a problem appearing in a stepwise manner, so that the translation 170 of the diffraction grating also moves in parallel in order to obtain a continuous wavelength tunable characteristic.

In other words, the external resonator type tunable light source device of FIG. 1 has a diffraction condition due to spatial displacement of the diffraction grating, that is, rotation and translation relative to the pivot point 105. It is a structure that can obtain the continuous (wavelength) variable characteristics by changing the.

The external resonator type tunable light source device of FIG. 1 has high advantages such as high output power, narrow linewidth, and wide tunability.

However, the external resonator type wavelength variable light source device of FIG. 1 is difficult to align between the semiconductor laser 110 and the diffraction grating 120, and mechanical vibration and pivot point 105 due to spatial movement of the diffraction grating 120 when the wavelength is variable. A wavelength shift problem occurs due to aging of the position. In particular, since the external resonator type wavelength variable light source device of FIG. 1 has a very low speed for variable wavelength, the external resonator type wavelength variable light source device is somewhat difficult to be used for optical communication and various application systems.

FIG. 2 is a view illustrating the structure of an external resonator type variable wavelength light source device of a Litman type among conventional variable wavelength light source devices.

Specifically, the tunable light source device is a semiconductor laser (laser diode LD) 210 coated with an anti-reflection film 12, an external diffraction grating 220, a lens 230, and reflections. It consists of the mirror 260.

A current is applied to the semiconductor laser 210 to generate the beam 250, and the beam 250 generated by the semiconductor laser 210 reaches the reflective mirror 260 through the lens 230 and the diffraction grating 220. Then, only the beam 250 incident perpendicularly to the reflection mirror 260 is reflected back to the diffraction grating 220.

The reflected beam 240 is fed back to the semiconductor laser 210 via the diffraction grating 220 and the lens 230 and outputs light Pout. The wavelength of the beam is determined according to the Litman diffraction grating formula of Equation 2 with respect to the incident angle α and the diffraction angle β with respect to the vertical line 200 of the plane of the diffraction grating in the structure of FIG. 2.

Where m is the diffraction order, λ is the wavelength, d is the period of the diffraction grating, α is the angle of incidence, and β is the diffraction angle.

Moving the reflection mirror 260 with respect to the pivot point 205 with respect to the above-described structure rotates 275, so that the diffraction angle β changes with respect to the same incident angle α. Equation 2 changes the wavelength.

If only the diffraction angle β is changed in the above-described structure, there is a problem in that the wavelength tunable characteristic appears as a step. Therefore, in order to obtain continuous wavelength tunable characteristics, the translation of the reflection mirror 260 is also performed in parallel. Make it move

In other words, the external resonator type tunable light source element of FIG. 2 has a spatial displacement, ie rotation 275, translation 270 of the reflection mirror 260 with respect to the pivot point 205. By changing the diffraction conditions (diffraction condition) is a structure that can obtain a continuous (wavelength) variable characteristics.

The external resonator type wavelength variable light source device of FIG. 2 has an advantage of being structurally stable compared to the structure of FIG. 1 since the diffraction grating 220 is fixed and only the reflection mirror 260 moves when the wavelength is variable.

However, the structure of FIG. 2 is also difficult to align between the semiconductor laser 210 and the diffraction grating 220 similarly to the structure of FIG. 1, and mechanical vibration and pivot point 205 due to spatial movement of the reflective mirror 260 when the wavelength is variable. ) Has a wavelength shift problem due to the aging of the position, and because the speed for the variable wavelength is very slow, it is somewhat difficult to be used in optical communication and various application systems.

In order to solve the slow wavelength variable speed of the external resonator type tunable light source device of FIGS. 1 and 2 described above, structures for varying the wavelength by electrical control have been proposed. For example, M. Kourogi et al. Described in "Optics Letters, vol. 25, No. 16, pp. 1165-1167, Aug. 15, 2000" as "continuous tuning of an electrically tunable external-cavity semiconductor laser." Instead of moving the diffraction grating for the wavelength variation, an AOM (Acouto-optic modulator) was inserted between the laser diode and the diffraction grating and the wavelength variation was made by using the beam deflection characteristic according to the frequency variation of the external electrical signal.

However, the structure proposed by M. Kourogi et al., 4, has a disadvantage that the volume of AOM is large, the insertion loss is large, and the amount of wavelength variation is only 2 nm.

In summary, the conventional tunable light source device that varies the wavelength through spatial variation of the diffraction grating has many problems in terms of reliability and speed.

In addition, the conventional bulk type tunable light source device having an electrically variable wavelength has a disadvantage in that alignment between the diffraction grating and the laser diode is difficult, and the volume of the device is large due to the insertion of the AOM.

An object of the present invention is to provide a tunable light source device that does not require additional optical components or light alignment by integrating bulk components of the optical structure.

Another technical problem of the present invention is that the diffraction grating made of a material (silicon, polymer, etc.) that can be stably manufactured in addition to the diffraction grating made of indium material can be easily hybridized, thereby reducing the optical coupling loss between the two materials. It is to provide a variable wavelength light source device that can minimize and increase the reliability of the device.

One embodiment of the wavelength variable light source device according to the present invention for achieving the above technical problem, transmits an optical signal having a predetermined wavelength band in one direction, and amplifies the optical signal of a predetermined wavelength of the wavelength band in the other direction An optical amplifier for outputting; A beam controller for moving an output path of the optical signal having the wavelength band; And one end of which is connected to the beam manipulator and has a straight line structure in which the optical signal having the wavelength band is spread and transmitted in a planar manner, and the other end reflects and diffracts the optical signal having the wavelength band to reinforce the single wavelength at one end. A waveguide formed of a concave diffraction grating to cause interference; and the constructive interference single wavelength has a linear trajectory and is fed back to the optical amplifier via the beam manipulator.

One embodiment of the wavelength variable light source device according to the present invention for achieving the above technical problem, transmits an optical signal having a predetermined wavelength band in one direction, and amplifies the optical signal of a predetermined wavelength of the wavelength band in the other direction An optical amplifier for outputting; One end is formed in a straight line structure connected to the optical amplifier so that the wavelength band optical signal is spread and transmitted in a planar manner, and the other end reflects and diffracts an optical signal having the wavelength band to generate constructive interference of the single wavelength at the one end. A waveguide formed by a concave diffraction grating; And a deflector positioned in the upper cladding layer of the waveguide and varying a degree of deflection of the optical signal having the wavelength band according to the amount of incident current. The reinforcement-interrupted single wavelength has a linear locus and passes through the deflector. It is characterized by being fed back to the amplifier.

According to an embodiment of the present invention, a wavelength variable light source device according to the present invention transmits an optical signal having a predetermined wavelength band in one direction and amplifies an optical signal having a first wavelength and a second single wavelength among the wavelength bands. A first optical amplifier for outputting in the other direction; A beam controller for moving the output path of the wavelength band optical signal; One end is formed in a straight line structure connected to the beam manipulator so that the wavelength band optical signal is spread and transmitted in a planar manner, and the other end reflects and diffracts an optical signal having the wavelength band so that the first single wavelength optical signal is connected to the beam manipulator. A waveguide formed by a concave diffraction grating that satisfies the Litman condition for generating constructive interference in a first portion and causing the constructive interference in a second portion of the one end; And a second optical amplifier for re-injecting the second single wavelength optical signal into the concave diffraction grating of the waveguide to be fed back to the first optical amplifier.

According to an embodiment of the present invention, a variable wavelength light source device according to the present invention transmits an optical signal having a predetermined wavelength band in one direction and amplifies an optical signal having a first wavelength and a second single wavelength among the wavelength bands. A first optical amplifier for outputting in the other direction; One end is connected to the first optical amplifier and is formed in a straight line structure so that the wavelength band optical signal is spread and transmitted in a planar manner, and the other end reflects and diffracts an optical signal having the wavelength band so that the first single wavelength optical signal is A waveguide formed by a concave diffraction grating which satisfies the Litman condition for generating constructive interference in a first portion of the first end and the constructive interference in the second single wavelength optical signal; A deflector positioned in an upper cladding layer of the waveguide and varying a degree of deflection of an optical signal having the wavelength band according to an amount of incident current; and reentering the second single wavelength optical signal into a concave diffraction grating of the waveguide. And a second optical amplifier for feeding back to the first optical amplifier.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

3 is a diagram illustrating a structure of a deflector integrated wavelength variable light source device including a Roland circle diffraction grating.

The structure includes an optical amplifier 310, a phase control unit 320, an optical deflector 330, and a concave diffraction grating 340 that are integrated into a single, external resonant wavelength. It is a device that operates with a variable laser.

In this structure, the optical optical amplifier, phase control unit, deflection unit, and concave grating are all integrated in a single substrate (InP, InP) and injected into the deflector. Due to the deflection characteristic of the waveguide beam according to the amount of current to be made, the angle of incidence on the diffraction grating is changed to change the wavelength.

The beam exiting from one end surface of the optical amplifier 310 is incident to the concave diffraction grating 340 via the phase adjuster 320 and the optical deflector 330.

The beams arriving at the concave diffraction grating 340 are reflected at respective diffraction grating planes due to the difference in refractive index between the semiconductor material and the air, and at the same time, the positions are different for each wavelength due to the diffraction characteristics of the concave grating grating. Gathered at At this time, the trajectories of the beams gathered according to the wavelength are present on the virtual circle 350, which is called a lowland circle 350.

In general, the above-mentioned effect is obtained when the radius of the concave diffraction grating becomes twice the radius of the Roland circle.

Therefore, when the end of the waveguide is positioned on the Roland circle in the above structure, the beam is diffracted at the concave diffraction grating, and only the beam corresponding to a specific wavelength is fed back to the optical amplifier 310. The left end face of the optical amplifier and the concave diffraction grating are The surface becomes a reflecting surface and is operated by an external resonant laser due to resonance.

On the other hand, the phase controller 320 may be inserted between the optical amplifier and the optical deflector. The phase controller serves to match the phase between the beam emitted from the optical amplifier and the beam entering the optical amplifier from the diffraction grating, and the phase of the resonant beam is changed by changing the refractive index of the medium by the phase adjusting current (IPCS). Will be adjusted.

4 is a structural diagram for explaining a variable characteristic of the wavelength tunable laser of FIG.

It shows beam characteristics when no electric signal is applied to the optical deflector 330, and the beams in which the optical gain is generated in the optical amplifier 310 pass through the optical deflector 330 at a wavelength of? Since the effective refractive index of the deflector 330 pattern and the peripheral region is the same, the beam refraction does not appear. The beams incident on the concave diffraction grating 340 are fed back to the optical amplifier 310 according to the incidence angle α according to the incidence angle α only.

Where m is the diffraction order,? Is the wavelength, n1 is the refractive index of the waveguide layer, and d is the period of the diffraction grating.

Therefore, the beams generated by the optical amplifier 310 are fed back only a specific wavelength λ1 from the concave diffraction grating. When the feedback characteristic of the process is equal to the loss of the entire device, resonance is generated to operate with a laser. Only the beam λ1 having a specific wavelength is emitted to the left end surface of the optical amplifier 310.

When the current is injected into the deflector, the refractive index of the core material in the deflection pattern is changed due to carrier-induced reflecrtive index variation.

In this case, when the beam passes through the region formed by the deflection pattern, reflection is generated based on Snell's Law at the interface between the region where the refractive index is changed and the region which is not changed.

The refraction causes the beam to change direction. Therefore, the deflected beam changes the incident angle to the concave grating and changes the wavelength fed back to the amplifier based on Equation (3).

Referring to FIG. 4B for the above description, an electric signal is applied to the optical deflector pattern 330 to show beam characteristics when the refractive index of the waveguide layer in the pattern is changed from n1 to n2.

The beams generated by the optical amplifier pass through the deflector pattern, and the beams undergo refraction as the refractive index of the core layer in the deflector changes. The source point of the refracted beams virtually passes through the Rowland circle, as shown in the drawing, and the incident angle of the refracted beams is changed from the α angle equivalently to the α 'angle.

 With the changed angle of incidence the wavelength of the diffracted beam changes from lambda 1 to lambda 2. The optical deflector 330 is made of a material having a first effective refractive index n1 so that a current is injected only into a deflection pattern region having a predetermined shape, or the periphery of a predetermined deflection pattern having a first effective refractive index n1. The material and the inside of the deflection pattern region may be configured to be bounded by a material having a second effective refractive index n 2, and a current may be injected only into the deflection pattern region so that the refractive index of the waveguide layer in the pattern is n 2 to n 3.

Therefore, the refractive index of the core material in the deflection pattern of the predetermined shape is changed by an external electric signal (current) so that the beam is deflected according to the refractive characteristic (Snell's law) with respect to the incident angle at the interface between the peripheral area and the deflection pattern area of the predetermined shape. Has characteristics.

The optical deflector 330 is designed such that the position of the point source of the beam emitted by the optical amplifier 310 moves virtually along the Rowland circle as the electrical signal in the deflector increases.

The shape of the optical deflector pattern may be designed in accordance with ray-optics or in terms of wave-point to fit the structure of the Laurent circle.

The monolithic diffraction grating cavity-wavelength laser has the advantages of high speed, stable and single integration for small wavelengths due to electrical control. In addition, since the waveguide is correctly positioned on the Roland circle, the light coupling characteristics between the beam spread from the Roland circle to the diffraction grating and the beam fed back to the Roland circle from the diffraction grating have excellent light output.

However, since the deflector is inserted in the path through which the beam passes, the light output is reduced due to the increased light loss when the current is injected into the deflector. In addition, the design of the deflector pattern structure is difficult and difficult to implement.

FIG. 5 is a diagram illustrating a structure of a beam adjuster integrated wavelength variable light source device including a Roland circle diffraction grating.

The beam adjuster integrated external resonator type variable wavelength light source device 500 includes a semiconductor optical amplifier (510), a beam steering unit (520), and a concave grating (530) having a single substrate (Indium). , InP), all of which are integrated, and the angle of incidence of the waveguide beam is changed by controlling the position of the waveguide beam according to the difference in the amount of current injected into the two electrodes in the beam controller.

 The refractive index changes according to the amount of application of the IBS1 current and the IBS2 current, and the change of the refractive index affects the incident angle of the beam. In other words, the beam manipulator serves as a prism.

As shown in FIG. 5, as the amount of current is applied, the effective refractive index of the core layer is lowered, and the beam output from the optical amplifier 510 is bent toward the side of applying a relatively low current because the beam is bent toward the higher refractive index.

FIG. 6 is a structural diagram illustrating a variable characteristic of the wavelength tunable laser of FIG. 5.

Specifically, the wavelength variable light source device (wavelength variable laser 500) of FIGS. 6 (a) and 6 (b) has a structure that satisfies the Littrow condition of Equation (3).

The variable wavelength light source device 500 illustrated in FIG. 6A is a semiconductor optical amplifier (SOA) 510, a beam steering unit 520, and a recess on a semiconductor substrate 501, such as InP. The diffraction grating 530 is implemented in a single integrated.

The semiconductor optical amplifier 510 may be configured of a semiconductor laser diode, and an ISOA current may be applied.

Two electrodes are configured in the beam controller 520, and electrical signals such as IBS1 current and IBS2 current may be applied to the two electrodes.

The concave diffraction grating 530 is located on one side of the substrate 501, and the diffraction grating is implemented on one side of the semiconductor substrate 501.

Although the concave diffraction grating 530 is not limited to a specific structure, it is shown in the form of a Rowland circle 540 for explanation, and the concave diffraction grating 535 based on the Laurent circle 540 is shown in FIG. b).

The point where the concave diffraction grating circle 535 and the Laurent circle 540 meet is called a pole (P), and the reference line 610 is the center (C) to the pole (P) of the concave diffraction grating circle 535. Becomes the line of. One side of the Laurent circle 540 is positioned in contact with the beam manipulator 520.

In the structure of FIG. 6A, the left end surface of the optical amplifier 510 and the concave diffraction grating 530 each have a reflective surface, and thus are formed as a resonator to operate in the form of a laser diode.

The beam 620 emitted from the optical amplifier 510 toward the diffraction grating 530 is incident on the pole P of the concave diffraction grating 530 via the beam manipulator 520. The beam 520 incident on the concave diffraction grating is fed back to the optical amplifier 510 at an angle equal to the incident angle α only based on the diffraction characteristic of the concave diffraction grating 530. Only the beam 600 of wavelength is output Pout1. The specific wavelength output is according to the Littrow diffraction grating formula of Equation 3.

Incident angle (alpha) represents the angle between the reference line 610 and the incident beam path, as shown to FIG. 6 (a) and FIG. 6 (b).

The beam controller 520 may include two electrodes therein, and may control the beam path by adjusting a difference in the amount of current applied to the two electrodes. Accordingly, the beam 620 in which the path is moved may be a concave diffraction grating ( The incident angle α incident on the 630 is changed.

The wavelength of the beam 620 diffracted based on Equation 3 is changed according to the change of the incident angle α.

The concave grating grating wavelength variable light source integrated with the beam manipulator has the advantages of fast, stable and single integration for small wavelengths due to electrical adjustment. In addition, the above-described structure has the advantage that the light output change is small because the light loss is reduced when the wavelength is changed because the current is injected around the path through which the beam passes.

The position at which the beam is steered should be located on the Roland circle, and the width of the beam manipulator is so wide that the electrodes in the beam manipulator are asymmetric. This distorts the shape of the steered beam in the beam manipulator and at the same time does not make the position of the beam clear on the Roland circle, which causes the beam to spread from the Roland circle to the diffraction grating and the beam fed back to the Roland circle from the diffraction grating. The light coupling property of the liver is deteriorated and thus has a disadvantage of low light output.

In summary, the low-land deflector integrated wavelength variable light source of the Roland circular structure described above with reference to FIGS. 3 and 4 has a large light output but a deflector is placed in a path through which the beam passes. Low light output fluctuation has a large disadvantage, and the Roland circle structure of the beam manipulator integrated wavelength variable light source described above in FIGS. Due to the asymmetry of the inner electrode has a disadvantage of low light output due to reduced coupling efficiency.

In addition, the aforementioned Roland circle-based concave diffraction grating integrated wavelength variable light source is fabricated on an indium substrate because all of the functional units are integrated.

However, in the implementation of the diffraction grating of the indium material described above, the etching characteristics are somewhat non-uniform, and the diffraction grating pattern is not precise and high loss is a problem.

Therefore, the diffraction grating may be made of silicon, polymer, and the like, which are capable of uniform etching characteristics and precise patterns, and the concave diffraction grating may be hybridly integrated with an indium material.

However, the interface is a lowland one, making hybrid integration virtually impossible.

FIG. 7 is a diagram illustrating a structure of a beam adjuster direct tunable light source element including a diffraction grating such that the trajectory of the tunable beam is linear according to the present invention.

In the variable wavelength light source device 700 illustrated in FIG. 7, a semiconductor optical amplifier (SOA) 710, a beam controller 720, and a concave diffraction grating 730 are disposed on a semiconductor substrate S, for example, InP. It is integrated.

The semiconductor optical amplifier 710 may be configured as a semiconductor laser diode, and an ISOA current may be applied.

Two electrodes are configured in the beam controller 720, and currents IBS1 and IBS2 may be applied.

The concave diffraction grating 730 is located at one side of the substrate 701. Basically similar to the structure proposed in FIG. 5, the wavelength variable element 700 according to the present invention has a structure such that the position of a beam diffracted at the grating 730 is a straight line rather than a concave diffraction grating structure based on a Roland circle. Has

Since the position of the beam is a straight line, the electrodes in the beam controller become symmetrical, and the position of the beam moves along the straight line according to the difference in the amount of current injected into each electrode.

8 is a view for explaining the principle of the diffraction grating structure such that the trajectory of the variable wavelength beam according to the present invention of FIG.

In addition to the structural variables θN and θN + 1 shown in FIG. 4, the variables are defined by Equation 4 below to simplify the expression.

The diffraction grating of FIG. 8 has constructive interference for a specific wavelength λ0 between point PN and PN + 1 with respect to point A, and is expressed by Equation 5 below.

Where neff is the effective refractive index in the waveguide and m is an integer. Equation 5 represents a relationship between RN + 1 and RN and may be expressed by Equation 6 below.

On the other hand, for the triangle connecting the points A, PN, B, is expressed by the first line of the following equation (7) based on the cosine two law.

Equation (7) represents the relationship between SN and (RN, θN), and since the second term in the root of the second line is a very small value, it is negligible, and if the root is used for Binominal approximation after Taylor expansion, It can also be expressed as the first line.

Similarly, with respect to point B, constructive interference conditions are established with respect to wavelength λ0 + Δλ (Δλ: wavelength change) in the same manner as in Equation 5 as in the first line of Equation 8 below.

Equation 8 represents a relationship between SN + 1 and SN or (RN, θN) in consideration of the result of Equation 7, and the first line of Equation 8 substitutes the result of Equation 7 Then we can approximate it like the second line.

Similarly to Equation 7, if applied to the points A, PN + 1, B also appears as in the following equation (9).

Equation 9 represents the relationship between SN + 1 and (RN + 1, θN + 1), and considering the result of Equation 6 above, it represents a relationship between SN + 1 and (RN, θN + 1). Equation (9) described above may be represented by a third line using an approximation method as in Equation (7), and may be represented by a fourth line based on the result of Equation 6.

In sum, four equations for the structural variables RN, RN + 1, SN, SN + 1, θN, θN + 1 based on the above-described structural relationships (Equations 6, 7, 8, 9) Neff is the value determined when the waveguide is determined, and d, R0, θ0 (= 0, m, λ0, Δλ) are design variables (already known).

When the diffraction grating order N is increased from 0 by the above-described relations, RN and θN are already known, and RN + 1, SN, SN + 1 and θN + 1 are the four equations (6). , 7, 8, and 9).

Meanwhile, the first line of Equation 10 may be represented by the relationship between the second line of Equation 8 and the fourth line of Equation 9.

 Since θN and θN + 1 are relatively small angles (up to 15 degrees), a linear approximation from a sine function can be expressed as the second line, and g is the diffraction grating period (design variable, the distance between PN and PN + 1). Appears. The relationship between the wavelength variable Δλ and the design variable can be expressed by the following Equation 11 from the equation of the second line of Equation 10 described above.

From Equation 11, it can be easily seen that the wavelength variable increases linearly with the structural variable as the d increases.

Equations 10 and 11 described above, including Equations 6 to 9, are derived to facilitate explanation, but the equations may be somewhat complicated because the approximation is not used in actual design.

In addition, since the relationship between the actual d and the wavelength variable amount? Λ is not linear for a certain design variable, g (diffraction grating period) can be artificially changed so that the relationship between d and the wavelength variable amount is linear.

9 is a wavelength variable of a structure in which a diffraction grating is made of silicon or polymer so that the trajectory of the variable wavelength beam according to the present invention of FIG. It is a figure which shows the structure of a light source element.

Etching characteristics are somewhat uneven in the implementation of diffraction gratings of indium materials, and high loss is a problem due to inaccurate diffraction grating patterns.

Therefore, the diffraction grating may be made of silicon, polymer, and the like, which are capable of uniform etching characteristics and precise patterns, and the concave diffraction grating may be hybridly integrated with an indium material.

The structure proposed in FIG. 3 or FIG. 5 has a low-land interface, which makes it difficult to perform hybrid integration.

However, in the wavelength variable element according to the present invention, since the trajectory of the beam diffracted in the concave diffraction grating is linear, hybrid integration is possible.

In addition, the indium material is cleanly cut along the line when pressure is applied perpendicular to the light output direction, and the reflectance is about 30%.

Therefore, an anti-reflection coating (930) is required on the cross-section of the indium material, and in some cases, the anti-reflection coating is required on the diffraction grating, and an impedance matching oil is required for smooth optical coupling characteristics. ) Can also be added.

10 is a diagram illustrating a structure of a deflector integrated wavelength variable light source device including a diffraction grating such that the trajectory of the variable wavelength beam according to the present invention is a straight line.

In the variable wavelength light source device including a diffraction grating such that the trajectory of the variable wavelength beam according to the present invention is a straight line, the deflector 1020 may be applied in an integrated form as shown in FIG. 3.

In general, the diffraction grating of the Laurent circle structure has an aberration, and thus a method of removing the aberration by adjusting the period of the diffraction grating is used.

The method of eliminating aberrations by adjusting the diffraction grating period has a problem of complicating the diffraction grating structure in the design. In addition, aberration can not be removed for higher order 5th order, and circular pattern design and manufacturing is not easy.

However, if the diffraction grating structure having a linear trajectory according to the present invention is adopted, the diffraction grating period can not only be adjusted during design, but also aberration can be completely eliminated, and the design and fabrication of the pattern in a straight pattern is relatively easy. have.

FIG. 11 is a diagram illustrating a structure of a beam adjuster integrated wavelength variable light source device including a diffraction grating for satisfying the Rietman condition and allowing the path of the variable wavelength beam to be straight.

The variable wavelength light source device (wavelength variable laser) 1100 of FIG. 11 has a structure satisfying the Littman condition of Equation 12, and is an angle incident on the diffraction grating due to the position shift of the beam according to the current injection of the beam controller. Since this changes, the wavelength is variable.

Where m is the diffraction order, λ is the wavelength, n1 is the refractive index of the waveguide layer, d is the period of the diffraction grating, α is the angle of incidence, β is the diffraction angle, and the angle of incidence α is the The angle between the reference line 1160 to the pole P and the path of the incident beam 1180, and the diffraction angle β is reflected by the reference line 1160 and the second optical amplifier 1140 or the optical waveguide 1140. Angle between beams 1190.

In the structure of FIG. 11, a diffraction grating designed to collect variable wavelength beams along a linear trajectory 1150 is applied.

 In FIG. 11, the wavelength of the incident angle α is changed due to the path movement of the beam due to the current injection of the beam manipulator with respect to the fixed diffraction angle β.

The beam 1180 emitted from the first optical amplifier SOA1 is incident on the concave diffraction grating 1130 via the beam controller 1120, and the incident beam 1180 is in accordance with the diffraction characteristics of the concave diffraction grating 1130. Only the beam 1190 corresponding to the specific wavelength is fed back to the additional second optical amplifiers SOA2 and 1140 or the optical waveguide 1140 at the angle of β and output (Pout2 and 1170).

In the structure of FIG. 11, since the left end surface of the first optical amplifiers SOA1 and 1110 and the left end surface of the second optical amplifier SOA2 each have a reflective surface, they are formed as a resonator to operate as a laser diode.

While the optical waveguide 1140 or the second optical amplifiers SOA2 and 1140 are additionally needed for guiding or amplifying the diffracted beam 1190 at the diffraction angle of β in the concave diffraction grating 1130, the wavelength tunable characteristic is also shown. More stable operation is possible compared to the structure of 7, and there is more choice in the design. In the structure of FIG. 7, there is only one optical output terminal, whereas in FIG. 11, since the optical output can be obtained in the cross section of the first optical amplifier 1110 and the optical waveguide 1140 or the second optical amplifier 1140, There will be more than one.

The additional optical amplifiers 1140 resonate and emit beams of different wavelengths as many as the number of channels. The wavelengths of the respective channels according to the optical waveguide or the optical amplifier 1140 are changed in wavelength by the current injection of the beam controller 1120.

When the wavelength interval between the channels according to the optical waveguide or the optical amplifier 1140 is fixed, the overall wavelength variable amount is the product of the wavelength variable amount of one channel according to the current injection of the beam controller 1120 and the number of channels. The wavelength can be increased by as much as possible.

 In the cross section of the waveguide 1140 or the second optical amplifier 1140, the optical outputs Pout2 and Poutn 1170 can be obtained by the wavelength region (the variable amount of wavelength by the beam controller) of each channel, and the first optical amplifier 1110 ), You can get the wavelength of all channels.

FIG. 12 is a view illustrating a structure of a wavelength tunable light source device having a diffraction grating made of silicon or polymer according to the present invention of FIG. 11 and having a single integrated material of an optical amplifier and a beam manipulator, an indium phosphorus and a hybrid integrated structure.

 Etching characteristics are somewhat uneven in the implementation of diffraction gratings of indium materials, and high loss is a problem due to inaccurate diffraction grating patterns.

Therefore, the diffraction grating may be made of silicon, polymer, and the like, which are capable of uniform etching characteristics and precise patterns, and the concave diffraction grating may be hybridly integrated with an indium material.

In addition, the indium material is cleanly cut along the line when pressure is applied perpendicular to the light output direction, and the reflectance is about 30%.

Therefore, anti-reflection coating 1230 (Anti-reflection coating) is required on the cross-section of the indium material, and in some cases, the anti-reflection coating is also required on the diffraction grating, and impedance matching oil for smooth optical coupling characteristics. ) Can also be added.

FIG. 13 illustrates a structure of a deflector integrated wavelength variable light source device including a diffraction grating which satisfies the Ritman condition according to the present invention and makes the trajectory of the variable wavelength beam linear.

In the present invention, the diffraction grating of the invention of FIG. 11 satisfies the Ritman condition and has the same operation principle as the beam manipulator integrated tunable light source element, but the deflecting part of the beam is implemented by the deflector 1320 rather than the beam manipulator. There is a difference.

FIG. 14 is a flowchart illustrating an operating principle of the tunable light source device of FIG. 7.

The optical amplifier outputs an optical signal having a predetermined wavelength band (S1400).

The output path of the optical signal having the wavelength band is deflected according to the amount of current applied from the deflector of the beam controller (S1410).

The concave diffraction grating having a predetermined lattice period reflects and diffracts the optical signal having the wavelength band such that constructive interference of a predetermined single wavelength of the wavelength band is generated in the deflection portion (S1420).

The predetermined single wavelength optical signal that is constructively interfered with the deflection portion is fed back to the optical amplifier (S1430).

The single wavelength optical signal fed back to the optical amplifier is amplified and output (S1440). Amplification of a single wavelength optical signal occurs when the gain of the optical signal to be amplified is equal to the optical loss in the optical amplifier.

FIG. 15 is a flowchart illustrating an operating principle of the tunable light source device of FIG. 11.

The first optical amplifier outputs an optical signal having a predetermined wavelength band in operation S1500.

The output path of the optical signal having the wavelength band is deflected according to the amount of current applied from the deflector of the beam controller (S1510).

The concave diffraction grating having a predetermined lattice period reflects and diffracts the optical signal having the wavelength band so that constructive interference occurs at one end of each of the waveguides having a linear structure for each wavelength (S1520).

At least one single wavelength optical signal of the single wavelength optical signals separated according to the wavelengths of the plurality of second optical amplifiers is reincident to the concave diffraction grating (S1530).

In the concave diffraction grating, the at least one single wavelength optical signal is fed back to the first optical amplifier, amplified and output (S1540).

Although the preferred embodiments of the present invention have been described above by way of example, the scope of the present invention is not limited to these specific embodiments, and may be appropriately changed within the scope of the claims.

As described above, in the variable wavelength light source device according to the present invention, an optical amplifier, a beam manipulator, and a concave diffraction grating are integrated, and the beams diffracted in the concave diffraction grating are gathered in a linear trajectory so that the two electrodes of the beam manipulator are symmetrical. At the same time, the position of the beam is cleared on a straight line, and the optical coupling property between the beam spread by the diffraction grating and the beam fed back to the cross section of the diffraction grating has excellent light output.

In addition, in addition to the diffraction grating made of an indium material, the diffraction grating made of a material that can be manufactured stably (silicon, polymer, etc.) can be easily hybridized, thereby minimizing optical coupling loss between the two materials, and the reliability of the device. To increase.

Claims (15)

An optical amplifier for transmitting an optical signal having a predetermined wavelength band in one direction and amplifying the optical signal having a predetermined single wavelength among the wavelength bands and outputting the optical signal in another direction; A beam controller for moving an output path of the optical signal having the wavelength band; And One end is formed in a straight line structure connected to the beam manipulator so that the optical signal having the wavelength band is spread and transmitted in a planar manner, and the other end reflects and diffracts the optical signal having the wavelength band, thereby constructing interference of the single wavelength at one end. And a waveguide formed of a concave diffraction grating to produce the concave diffraction grating. The single wavelength having the constructive interference has a linear locus and is fed back to the optical amplifier via the beam manipulator. The method of claim 1, The beam manipulator has a waveguide structure composed of a lower cladding layer, a core, and an upper cladding layer, and has a deflection degree of an optical signal having the wavelength band according to the amount of current applied to two electrode plates arranged at regular intervals on the upper cladding layer. A variable wavelength light source device, characterized in that different. The method of claim 1, And the optical amplifier, the beam manipulator, and the waveguide are integrated on a single substrate. The method of claim 1, And the optical amplifier and the beam manipulator are integrated on a first substrate of indium, and the waveguide is integrated on a second substrate of any one of a silicon series and a polymer series. An optical amplifier for transmitting an optical signal having a predetermined wavelength band in one direction and amplifying the optical signal having a predetermined single wavelength among the wavelength bands and outputting the optical signal in another direction; One end is formed in a straight line structure connected to the optical amplifier so that the wavelength band optical signal is spread and transmitted in a planar manner, and the other end reflects and diffracts an optical signal having the wavelength band to generate constructive interference of the single wavelength at the one end. A waveguide formed by a concave diffraction grating; And A deflector positioned in an upper cladding layer of the waveguide and varying a degree of deflection of an optical signal having the wavelength band according to an amount of incident current, including the reinforcement-interrupted single wavelength having a linear trajectory and passing through the deflector; The variable wavelength light source device characterized in that the feedback. The method of claim 5, And a phase controller positioned at an intermediate end of the optical amplifier and the waveguide to match a phase of an optical signal of a single wavelength returned from the concave diffraction grating to the optical amplifier and an optical signal output from the optical amplifier. A variable wavelength light source element. The method of claim 5, And the optical amplifier and the waveguide are integrated in a single substrate. The method of claim 5, The optical amplifier is integrated in the first substrate of the indium series, the waveguide is a variable wavelength light source device, characterized in that integrated on the second substrate of any one of the silicon series and polymer series. The method according to claim 1 or 5, And the concave diffraction grating satisfies the retro diffraction grating condition. The method according to claim 1 or 5, And the concave diffraction grating satisfies the Ritman diffraction grating condition. The method according to claim 1 or 5, The concave diffraction grating satisfies the Ritman diffraction grating condition, and is reflected and diffracted from the concave diffraction grating, and a plurality of single wavelength lights having constructive interference at different positions of one end of the waveguide for each wavelength of the optical signal having the wavelength band. And a plurality of single mode waveguides for outputting signals. A first optical amplifier which transmits an optical signal having a predetermined wavelength band in one direction and amplifies the optical signals of the first and second single wavelengths among the wavelength bands and outputs them in the other direction; A beam controller for moving the output path of the wavelength band optical signal; One end is formed in a straight line structure connected to the beam manipulator so that the wavelength band optical signal is spread and transmitted in a planar manner, and the other end reflects and diffracts an optical signal having the wavelength band so that the first single wavelength optical signal is connected to the beam manipulator. A waveguide formed by a concave diffraction grating that satisfies the Litman condition for generating constructive interference in a first portion and causing the constructive interference in a second portion of the one end; And And a second optical amplifier for re-injecting the second single wavelength optical signal into the concave diffraction grating of the waveguide so as to be fed back to the first optical amplifier. The method of claim 12, The first optical amplifier, the second optical amplifier, and the beam controller are integrated on a first substrate of an indium series, and the waveguide is integrated on a second substrate of any one of a silicon series and a polymer series. Tunable light source device. A first optical amplifier which transmits an optical signal having a predetermined wavelength band in one direction and amplifies the optical signals of the first and second single wavelengths among the wavelength bands and outputs them in the other direction; One end is connected to the first optical amplifier and is formed in a straight line structure so that the wavelength band optical signal is spread and transmitted in a planar manner, and the other end reflects and diffracts an optical signal having the wavelength band so that the first single wavelength optical signal is A waveguide formed by a concave diffraction grating which satisfies the Litman condition for generating constructive interference in a first portion of the first end and the constructive interference in the second single wavelength optical signal; A deflector positioned in an upper cladding layer of the waveguide and varying a degree of deflection of an optical signal having the wavelength band according to an amount of incident current; and And a second optical amplifier for re-injecting the second single wavelength optical signal into the concave diffraction grating of the waveguide so as to be fed back to the first optical amplifier. The method of claim 14, Wherein the first optical amplifier and the second optical amplifier are integrated on a first substrate of indium series, and the waveguide is integrated on a second substrate of any one of a silicon series and a polymer series. .

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