JP2001007439A - Widely wavelength tunable integrated semiconductor device and method for widely wavelength tuning semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for widely wavelength tunable integrated semiconductor device and laser by which the manufacture can be easily done, and a tuning in a wide range is possible and the loss of laser output is low. SOLUTION: The semiconductor device is provided with a semiconductor substrate and plural sections 500, 510, 530 and 540 on the substrate which are interconnected. At least two sections 500 and 510 are resonators each of which includes a wave guide path system, has several resonance maximum points spaced from one another and providing the maximum resonance at a relative wavelength. At least two spaces between resonance maximum points of each section are not essentially equal, and at least one resonance maximum point of each of the two sections 500 and 510 which are resonators overlaps with each other. Manufacturing process is similar to that of a (S) SG-DBR laser, and the output power does not pass through a long passive region.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-section integrated semiconductor device or laser having a resonant section that is either a distributed reflective or transmissive section. The invention also relates to a method for a semiconductor device or laser tunable over a wide range of wavelengths.

[0002]

BACKGROUND OF THE INVENTION The tuning of conventional distributed Bragg reflection (DBR) semiconductor lasers is limited to the fact that the relative tuning range is limited to a relative change in the refractive index of the tuning region. This results in a tuning range of 10 under normal operating conditions.
nm cannot be exceeded. This is substantially smaller than the potential bandwidth of about 100 nm, which is limited by the width of the gain curve. Such a conventional DBR laser is used to generate radiation, for example a light beam, by spontaneous emission over a bandwidth around one center frequency.
It can be functionally characterized as comprising a first part, which is an active section with two sides. The first portion guides the radiation or light beam. The conventional DBR laser further has two reflectors.
The reflector borders the active section having the two sides, one border on each side.

[0003] The problem of limited selectivity is described by Wolf (Wo).
lf) Recognized by others (European Transactions on Telecommunications and Related Technology, 4 (1993), No. 6, (Eu
ropean Transactions on Telecommunications and Rela
ted Technology, 4 (1993), No. 6)), a laser structure with two parallel waveguides without grating is shown in FIG.
0. These two parallel waveguides cannot be considered as resonators, and in fact the spectra (illustrated in FIGS. 10b and c) show comb-shaped mode spectra corresponding to arms B and A, but they are A, the comb mode spectrum of the gain section and the reflector R, or the arm B, the gain section and the reflector R
One of the comb-shaped mode spectra. Since the spacing between spectral lines is determined by the length of the structure, it can be seen that a much smaller spacing results in lower selectivity and lower tunability.

Heretofore, several advanced laser structures with extended tuning range have been proposed. See, for example, the Y-Laser (M. Kuznetsov, P. Verlangieri, A. G. Dentai, C. H. Joiner, and C. A. Bourse, Journal of the Design of Broadly Tunable Semiconductor Three-Branch Lasers).・ Light Wave Technology, 1994, Volume 12, Volume 12
No., p. 2100-2106, M. Kuznetsov, P. Verl
angieri, AG Dentai, CH Joyner, and CABurr
us, “Design of widely tunable semiconductor three-
branch lasers, ”J. Lightwave Technol., vol. 12, no.
12, pp. 2100-2106, 1994), twin-guide lasers coupled in the same direction (MC Aman and S. Elek, "Tunable laser diodes using a transverse tuning scheme", Journal Lightwave Technology) 1993, Vol. 11, No. 7, p.
182, M. -C. Amann, and S. Illek, “Tunable las
er diode utilizing transverse tuning scheme, ”J. l
ightwave Technol., vol.11, no.7, pp.1168-1182, 199
3) Sampled grating (SG) DBR lasers (Buy Jayalaman, Zed M. Chan, and L. A. Cordren, "Theory of extended tuning range semiconductor lasers with sampled gratings." , Design and Performance, IEEE Journal Quantum Electronics, 1993, Vol. 29, No. 6,
p. 1824-1834, V. Jayaraman, ZM Chuan
g, and LA Coldren, “Theory, design and performa
nce of extended tuning range semiconductor lasers
with sampled grating, ”IEEE J. Quantum Electron.,
vol. 29, no. 6, pp. 1824-1834, 1993), superstructure grating (SSG) DBR lasers (H. Ishii, H. Tanobe, F. Kano, W. Tomori, W. Kondo, and W. Yoshikuni) “Superstructure grating (S
SG) Quasi-continuous wavelength tuning in DBR laser "IEEE
E Journal Quantum Electronics, 199
6 years, Vol. 32, No. 3, p. 433-440, H. Is
hii, H. Tanobe, F. Kano, Y. Tohmori, Y. Kondo, and
Y. Yoshikuni, “Quasicontinuous wavelength tuning i
n super-structure-grating (SSG) DBR laseres, ”IEE
E J. Quantum Electron., Vol.32, no.3, pp.433-440,
1996), and a grating-assisted coupler (GCSR) laser with a sampled reflector on the back (M. Eberg, Es. Nilsson, K. Strobel, El. Beckbom, and T. Klinga, InGaAs with sampled grating reflector
74 nm wavelength tuning range of the same direction coupler laser assisted by the sP / InP vertical grating "IEEE
Photonics Technology Letters, 1993, Vol. 5, No. 7, p. 735-738, M. Oberg, S. Ni
lsson, K. Streubel, L. Backbom, and T. Klinga, “74
nm wavelength tuning range of an InGaAsP / InP vert
ical grating assisted codirectional coupler laser
with rearsampled grating reflector, ”IEEE Photon.
Technol. Lett., Vol.5, no.7, pp.735-738, 1993). In the first two types of devices, a trade-off must be made between tuning range and spectral purity (the magnitude of the side mode compression ratio (SMSR) over the tuning range width). So recently, the attention of many studies has
(S) It was poured into SG-DBR and GCSR lasers.

[0005] A sampled grating DBR laser comprises two sampled gratings that exhibit a comb-like reflectance spectrum with slightly different peaks spaced from each other for different sampling periods. Alternatively, other grating shapes can be used, and these are generally referred to as "superstructure gratings" (S
SG). This type of laser has about 100n
It is manufactured in the tuning range up to m. By injecting current into the two DBR sections, the device is operated such that the peaks of the front and rear reflectance comb characteristics are aligned with the desired wavelength. The phase section is used to align the longitudinal cavity mode with the two reflector peaks.
The disadvantage of the (S) SG-DBR approach is that the combined light from the laser must pass through long passive or inactive regions, leading to losses.
Also, the losses in the two reflective sections increase with the amount of current injected into those sections, leading to an output power that depends on the tuning current.

[0006] SG-DBR and SSG-DBR lasers are functionally equipped with an active region having two sides for light generation and two reflectors, one on each side of the active region. The reflector has a reflection characteristic with a plurality of reflection peaks. The property has a plurality of points of maximum reflection spaced from each other that provide a maximum reflection of the relevant wavelength. Such properties can be obtained with a sampled grating exhibiting a comb-like reflection spectrum or with a so-called super-grating. The grating or supergrating can also be characterized as a distributed reflector.

[0007] The sampled grating is a waveguide system having a periodically destroyed short-period structure including short-period stripped regions alternating with non-striped regions. It can be described as a structure. The supergrating is a diffraction grating having a plurality of repeating unit regions, each having a fixed length, thereby forming a modulation period, and each of the repeating unit regions along a direction of light transmission in the laser. At least one parameter that determines the reflectivity of the grating that varies with its position, and wherein the grating extends for at least two modulation periods. Reference is made to U.S. Pat. No. 5,325,392 concerning distributed reflectors and wavelength tunable semiconductor lasers, which is hereby incorporated by reference.

[0008]

The SG-DBR and SSG-DBR lasers use constructive interference with different periodicities of the periodic characteristics of the reflectors located on different sides of the active section and have a wide range. Get the tunability of.
The arrangement of the plurality of peaks of the reflector is such that the intervals between the reflection maximum points of the reflector are different or not essentially equal;
It can be described by explicitly stating that only one of the reflections of each reflector corresponds to the wavelength of the generated light beam. Reference is made to U.S. Pat. No. 4,896,325 for a multi-section tunable laser with different multi-element mirrors, which is hereby incorporated by reference.

[0009] Since the structure of the reflector leads to a long inactive section, this leads to a power loss in the laser output.

Other lasers using the same direction coupler easily have a very wide tuning range, but there is insufficient compression of nearby longitudinal modes. Widely tunable but poorly selectable same-directional coupler and single (S) SG
The combination with the reflector provides both a wide range of tuning and good side mode compression. Further, the light output signal does not pass through the passive area. Again, 100 nm tuning is achieved. Unfortunately, such structures are somewhat complex in manufacturing and require at least five growth stages. US Patent No. 5,62 for an integrated tunable filter
No. 1,828, which is hereby incorporated by reference.

[0011] EP-A-0926787 describes a series of strongly complex coupled DFB lasers. In the disclosed structure, the grating is made in the active section. The grating is selected such that no substantial interaction between the lasers, characterized as grating-formed active sections, is obtained in the series. Although the disclosed structure allows for the simultaneous generation of multiple wavelengths, it does not address selectivity and tunability issues.

A parallel structure having a plurality of waveguides is disclosed in Japanese Patent Publication Abstract, Vol. 13, No. 026, January 20, 1989, Japanese Patent Application Laid-Open No. 63-229796 (Fujitsu Limited) (PATENT ABSTRACT OF). JAPAN, vol.013, no.026,
20 January 1989, JP 63 229796 (Fujitsu ltd.)). The disclosed structure again allows for emission of multiple wavelengths, but does not address the issue of tunability. The optical switch is operated to select the waveguides, so that no simultaneous optical connection between the waveguides is obtained.

It is an object of the present invention to disclose a laser structure that is easy to manufacture, is tunable over a wide range, and has low loss in laser output power.

[0014]

According to the present invention, (S)
Another laser structure, apparatus or device is disclosed that has potentially the same tuning performance as SG-DBR and GCSR lasers and whose output power does not pass through long passive regions.

An integrated / semiconductor tunable laser is disclosed comprising a substrate of semiconductor material, an active section having two sides on the substrate, and a plurality of sections on the substrate. You. The laser can be referred to as a multi-section integrated semiconductor laser. The active region emits, for example, radiation, but is not limited to the range of light emission. All the above sections are connected to one side of the active section. this is,
Note that they do not imply that they are directly attached to the active section. In the case of light emission, the connection can be referred to as an optical connection. At least two of the connections include a waveguide system. Each of the above sections characterizes a resonator.

These resonance sections have a spectrum with a plurality of maximum resonance points spaced from one another. They are either themselves filters or reflectors having a comb-like mode spectrum.

The resonator used in the present invention has a resonance characteristic having a plurality of resonance peaks. Alternatively, the resonator can be said to have a plurality of spaced resonance maxima that provide the maximum resonance at the associated wavelength. The transmission filter used in the present invention has transmission characteristics having a plurality of transmission peaks. Alternatively, the transmission filter may be said to have a plurality of transmission maxima spaced apart that provide the maximum transmission of the relevant wavelength. The reflector used in the present invention has a reflection characteristic having a plurality of reflection peaks. Alternatively, the reflector may be said to have a plurality of spaced reflection maxima that provide the maximum reflection of the relevant wavelength.

The spacing of the resonance maxima corresponding to the transmission or reflection maxima of at least two of the sections is selected to be essentially unequal or different. The laser is therefore called an integrated semiconductor laser with different reflective or transmissive sections. The transmission and reflection characteristics of the transmission filter and the reflector are positioned relative to each other such that at least one of the transmission or reflection maxima of each of the two sections overlap each other. This means that the sections have at least one transmission or reflection maximum at the same first frequency. Due to the different spacing of the transmission or reflection maxima, a small shift of one of the transmission or reflection characteristics results in a maximum overlap of at least one other transmission or reflection of each of the two sections. can get. The sections then have in common at least one second frequency, which may be significantly different from the first frequency. The shift can be attributed to the injection of current into the transmissive or reflective section. The laser may be said to have means for injecting current into some of the plurality of sections, so that the transmission or reflection properties are shifted in wavelength. The overlapping maxima characterize the wavelengths of the lasers. With a small shift in at least one resonance characteristic, the device jumps from a first set of multiple laser wavelengths to another set of multiple laser wavelengths. Thus, the spacing of the maximum resonance points is essentially determined by the grating instead of the section length.

The active section generates a radiation or light beam upon emission, and the apparatus emits light having a wavelength of the emitted light beam corresponding to the overlapping maximum of the plurality of transmission filters or reflectors. It can be said that a laser beam is emitted. Thus, the active section generates a radiation or light beam by spontaneous emission over a bandwidth around the center frequency, guides the radiation or light beam and has a (light) amplification effect. The emitted radiation or light beam does not pass through the plurality of sections. The combination of the plurality of sections with combined reflection and the (light) amplification of the active section produces laser light at the set of laser wavelengths. The fact that small shifts in the resonance properties result in large differences in the set of laser wavelengths results in optical lasers with a wide range of tunability. Hence, the laser is called an integrated semiconductor laser tunable over a wide range of wavelengths.

According to one preferred embodiment of the invention, the active radiation generating section is connected on one side to a plurality of grating sections, but the plurality of gratings are not included in the active section.
Further, the plurality of gratings are selected such that a substantial interaction between the spectra of the plurality of gratings can be used, since this is the operating principle used to improve selectivity. . Thus, at least one of the resonances of each of the two sections overlaps with each other.

In one preferred embodiment of the invention, only one of said resonance maxima overlaps. The active section then generates a radiation or light beam by emission, and the device comprises an emission having a wavelength of the emitted light beam corresponding to the overlapping maximum of the plurality of transmission filters or reflectors. It can be said that a laser beam is emitted. The combination of the plurality of sections having a combined reflection action with a single reflection wavelength and the (optical) amplification action of the active section is such that the single section is characterized by the overlapping resonance maxima. At the reflection wavelength,
Generates laser light.

In one preferred embodiment of the present invention, at least one of said plurality of sections is inactive. This means that such inert sections do not generate a light beam by emission.

In one preferred embodiment of the invention, at least one of said plurality of sections is active. This means that such active sections also generate a light beam by emission.

[0024] In one preferred embodiment of the invention, at least one of the waveguide systems comprises periodically stripped regions comprising short-period stripped regions alternating with non-striped regions. Having a short period structure. Such a waveguide system is also called a distributed type, and thus the laser is called a semiconductor laser with a distributed reflective or transmissive section. In the present invention, two such waveguides are found on the same side of the active region.

In one preferred embodiment of the invention, at least one of said waveguide systems comprises a diffraction grating, each having a length and having a plurality of repeating unit regions, thereby forming a modulation period; At least one parameter that determines the reflection or transmission of light of the diffraction grating that varies with its position in each of the repeating unit regions along the direction of light transmission in the laser, wherein the diffraction grating has at least It extends for two modulation periods.

In one preferred embodiment of the invention, at least one of said waveguide systems is a ring resonator.

In one preferred embodiment of the present invention, a laser is used to optically connect a part of the plurality of sections and connect a part of the plurality of sections to the active section. Is further provided.

In one preferred embodiment of the invention, the laser is a cascade of the active section and the plurality of sections.

In one preferred embodiment of the invention, the laser is a connection of the active section to one single port side of a power splitter, and a multi-section, other multi-port of the power splitter. It is a parallel connection to the side.

In one preferred embodiment of the invention, the laser comprises a reciprocating cavity phase and a phase section used to adjust the laser mode wavelength of the laser.

[0031]

DETAILED DESCRIPTION In the following description, several embodiments of the present invention are set forth. It must be pointed out that the scope of the invention is described by the claims.

The present invention discloses another laser structure, potentially with the same performance as (S) SG-DBR and GCSR lasers, with the output power not passing through long passive regions. In the above device, there is a passive or inactive area on only one side of the active area.

Prior art distributed Bragg reflectors (D
The principle scheme of a BR) semiconductor laser is shown in FIG. A schematic diagram of such a laser is shown in the front (50
0) Illustrated in FIG. 1 showing a reflector, a rear reflector (510), an AR (anti-reflective coating), an active section (530), and a phase section (540).
The tuning of the laser is limited by the fact that the relative tuning range (360) is limited to relative changes in the refractive index of the tuning region. This means that under normal operating conditions the tuning range cannot exceed 10 nm. This is substantially limited to the width of the gain curve (350),
Narrower than a potential bandwidth of about 100 nm. Such a conventional DBR laser has characteristics (340) of the laser.
Over a bandwidth around a certain center frequency (370), which is a two-sided active section (300) for generating a light beam (310) by spontaneous emission. It can be functionally characterized as comprising. The first portion guides the light beam. Such a conventional DBR laser further has two reflectors (330) (320). The reflector borders the two-sided active section (300), one border on each side.

The classical laser structure is: (i) generating a light beam by spontaneous emission over a bandwidth around a certain center frequency, guiding the light beam and the active section performing an optical amplification action Active section with two sides /
Region and (ii) two (inactive or passive) sections / regions acting as reflectors. The active section borders the two reflectors.

Also, in addition to reflective sections / regions (inactive or passive), there are a plurality of sections having transmission properties.

The present invention can be characterized as having a two-sided active section / region (just like a classical laser) and a plurality of sections / regions. The plurality of sections / regions characterize a network of sections / regions. The section / area network is connected to one side of the active area. The network comprises at least two resonator regions / sections. The region / section of the resonator can be each of a plurality of reflectors and a plurality of regions / sections having transmission characteristics. The active element (30) and the plurality of sections (50) (9
The basic scheme of a laser according to the invention comprising 0) (100) (110) and thus either a plurality of transmission filters or a plurality of reflectors is illustrated in FIG.

The present invention comprises (i) a substrate made of a semiconductor material, and (ii) an active section having two sides on the substrate, wherein the active section has a bandwidth around a certain center frequency. Producing radiation by spontaneous emission,
Guiding the radiation, the active section having an amplifying action, and (iii) comprising a plurality of sections on the substrate, all of the plurality of sections being connected to one side of the active section; At least two of the sections are characterized as devices that include a waveguide system that characterizes either a transmission filter or a reflector. The apparatus may further include a plurality of power splitters used to interconnect some of the plurality of inactive sections and connect some of the plurality of sections to the active section. The sections can be either active or inactive.

When the device generates a light beam, the connection with the active section of the network is an optical connection. The connections of the sections are then also optical connections. Thus, the device is referred to as a tunable integrated / semiconductor optical laser. The amplification is then called optical amplification. Then, the active section also guides the light beam.

In the present invention, a plurality of specific reflectors and sections having transmission characteristics are used. The reflector and the section having the transmission characteristics are generally called a resonator. The reflective and transmissive sections are functionally characterized as having reflective or transmissive properties having a plurality of reflective or transmissive peaks, commonly referred to as resonance peaks. The reflection or transmission characteristic comprises a plurality of spaced reflection or transmission maxima that provide the maximum reflection or transmission of the relevant wavelength. Thus, the resonance characteristic has a plurality of spectral response peaks, preferably narrow spectral response peaks. The above-mentioned resonator characteristics mean that all the resonance frequencies have an interval from each other by the same value, and are regular (regular) that is periodic,
Or it can be either irregular, meaning that there is no fixed spacing between the resonance frequencies. Irregular can be a random pattern of resonant frequencies or some structured pattern.

Such a characteristic can be obtained using a sampled grating exhibiting the reflection or transmission spectrum of the comb characteristic, or using a so-called supergrating. The grating or supergrating can also be characterized as a distributed reflector or transmission section.

The sampled grating has a periodically destroyed short-period structure, including short-period stripped regions alternating with non-striped regions. It can be described as a structure. The supergrating is a diffraction grating having a plurality of repeating unit regions, each having a fixed length, thereby forming a modulation period, and each of the repeating unit regions along a direction of light transmission in the laser. At least one parameter that determines the reflection or transmission of light of the diffraction grating that varies with its position, the diffraction grating extending by at least two modulation periods. .

In the present invention, another plurality of sections having transmission characteristics based on the ring resonator are used. Such a ring resonator has a comb-shaped transmission characteristic (FIG. 5). The operation of the ring resonator is a classic
Similar to the operation of a Perot resonator, this can be easily understood if the cross-coupling of the two couplers in the ring is considered as a transmission mirror in the FP-resonator.

In the prior art, constructive interference of the periodic characteristics of a plurality of reflectors with different periodicities located on different sides of the active section is used to obtain a wide range of tunability. When the structure of the reflector reaches a long inactive region, this results in a power loss of the laser output.

In the present invention, constructive interference of the periodic properties of multiple sections, either reflective or transmissive, having different periodicities and located on the same side of the active section is used. This approach results in a wide range of tunability of the laser. Even when the reflectors are structurally long inert sections,
This is not detrimental to the output power of the laser, since they are only located on a single side of the active section. The present invention is always a low loss window.

Thus, the present invention provides that the spacing of at least two transmission or reflection maxima in each (inactive or regular active) section is essentially unequal or different, and Inactive or regular activity)
It can be further characterized by explicitly stating that at least one of the transmission or reflection of the section corresponds to the wavelength of the generated light beam. This correspondence is obtained by having at least one of the resonance peaks of at least two overlapping or coincident sections.

The combination of the sections can be regarded as a combined reflector having a combined reflective action. The light amplification action of the active section and the combined reflection action of the combined reflector generate laser light at at least one reflection wavelength of the combined reflector.

FIG. 6 illustrates an example of a possible configuration, but the invention is not limited to this. The active section (30)
Optically multiple sections (12
0), the sections are composed of a transmission filter (50) and three reflectors (90) (100) (1).
10). Laser light (10) exits the laser from the other side of the active section. (20) shows the amplification action in the active section (10). The above connection (4
0), (60), (70) and (80) refer to optical interconnectivity and should not be considered physical connections.

The transmission filter used in the present invention has a transmission characteristic (150) having a plurality of transmission peaks. Alternatively, the transmission filter can be said to have a plurality of transmission maxima spaced apart (interval (130)) that provide maximum transmission of the associated wavelength. The reflector used in the present invention has a reflection characteristic (160) having a plurality of reflection peaks. Instead, the reflector can be said to have a plurality of reflection maxima spaced apart (interval period (140)) providing the maximum reflection of the relevant wavelength. The distance (130) (14) between the transmission or reflection maximum points of at least two of the sections.
0) is chosen differently. Therefore, the laser
It is called an integrated semiconductor laser with different reflective or transmissive sections. The transmission and reflection characteristics of the transmission filters and reflectors are positioned such that only one transmission or reflection maximum of each section overlaps, which is intended to have a transmission or reflection maximum at the same frequency. are doing. The different spacing of the transmission or reflection maxima results in an optical laser having a wide range of tunability from a small shift of one of the transmission or reflection maxima. Hence, the laser is called an integrated semiconductor laser tunable over a wide range of wavelengths. The shift can be attributed to the injection of current into the transmissive or reflective section. The laser may include means for injecting current into a portion of the plurality of sections, such that the transmission or reflection characteristics may be shifted with respect to wavelength.

The structure shown in FIG.
Is achieved by using a power splitter (200) to connect to the sections (90) (100) (110). The power splitter has a single port side (the side connected to (50)) and a multi-port side having three ports (the side connected to (90), (100), and (110)).

A schematic diagram of a prior art GCSR laser structure includes an active section (600), a coupler section (6).
10), phase section (620), and reflector (63)
0) and the cross section of said section. The coupler section and the reflector section have essentially different resonance characteristics. The coupler sections do not have resonance maxima spaced from one another.

In the first embodiment, the active region (70
0), two reflectors (71) located on the same side.
0), (720), a Y-type structure as in FIG. 3 is proposed. These two reflectors use sampled or superstructured gratings to provide a comb characteristic of reflectivity with different periods and their design is based on (S) SG-
Same as DBR laser. Power splitter (73
0) is used to split / combine light exiting / entering the active region. Two phase control sections (740), (750) are illustrated in FIG. One provides a precise phase relationship between the signals reflected by the two reflectors, while the second provides control of the overall phase of the combined reflected signal. According to an alternative embodiment, a separate phase control section can be located on each of the Y-arms. The branches of the Y-type structure can all be active and active, thus preventing the (technically more complex) transition from an active and active waveguide to a passive one. However, this has the disadvantage that the device becomes more difficult to control,
This is due to a mix of power and wavelength controls.
Therefore, passive waveguides for both branches of the Y-shaped structure are preferred.

In the second embodiment, there is proposed a second structure whose top view can be seen in FIG. In this configuration, multiple reflectors (440) (including reflectors (410, 420, 430)) are located on the same side of the active area. At least two of the reflectors use a sampled or superstructured grating to provide a comb characteristic of reflectivity. At least two of the reflectors have a comb characteristic of reflectivity with different periods. The design of the reflector is identical to that of the (S) SG-DBR laser. A power splitter (450) is used to split and combine light exiting / entering the active area. A phase control section can be introduced. In one configuration, one phase control section is located between the active area and the plurality of reflectors, and in all but one reflector a phase control section is provided.
In other configurations, only a phase control section is provided in the plurality of reflectors.

In the third embodiment, a third structure shown in FIG. 4 is proposed. The reflector has an active section (830), a ring resonator (800) with comb-like transmission properties (FIG. 5), and a (S) SG- with a potentially even anti-reflective coating (820). Reflector (81
0). The operation of the ring resonator is similar to that of a classic Fabry-Perot resonator,
It can be easily understood if the cross-coupling of the two couplers in the ring is considered as a transmission mirror in the FP-resonator. Again, tuning is based on the "Vernier" principle, like a conventional (S) SG-DBR laser. Ring resonators and (S) SG-reflectors are designed to have slightly different peak spacings in each of their transmission and reflection properties, so that the two peaks overlap at or at a wavelength that overlaps each other. Laser light is generated in the vicinity. The phase section used to align the longitudinal cavity mode to two aligned peaks is also included in this structure. It is located either between the active section and the ring resonator or between the ring and the (S) SG-reflector.

In the fourth embodiment, a fourth structure shown in FIG. 9 is proposed. This structure corresponds to the filter (9
10) A plurality of transmission filters (940) including (920)
With an active area (900) bordering on one side a cascade of sections, the connection terminating at a reflector (930). At least two of the sections, which are either transmission filters or reflectors, have a comb-like transmission characteristic. At least two of the sections, either transmission filters or reflectors, are designed to have slightly different peak spacing in their properties. A phase section can be located between any of the plurality of sections and between the active section and the plurality of sections. The transmission filter can be either an (S) SG-transmission filter or a ring resonator. The reflector is an (S) SG-reflector.

A key feature of any structure using the proposed Y-type and ring structures, and a combination of principles based on the proposed Y-type and ring structures, is that light is emitted directly from the active region; It does not pass through the passive area. This is expected to result in higher efficiency and a lower power change during tuning. Typical reflectors can be designed to have a uniform envelope of the reflection peak. These designs require long passive waveguides and the reflectivity at the reflection peak is very high. Both of these factors
In a two sided reflector structure, the efficiency is reduced. In all proposed structures, the output power does not pass through the reflector, so high efficiency can be expected, and high reflectivity is now an advantage. Thus, in the present invention, all the sections are optically connected to one side of the active area.

Since the reflector is preferably passive,
The Y-type structure (of the first embodiment) and the structure of the second embodiment are not harmed by the control problems known from the prior art that appear in Y-type lasers.

The performance related to tuning and output power is determined by GC
Expected to be similar to that of SR lasers, but easier to manufacture. The number of steps is the same as SG / SSG, but less than GCSR laser. Except for the mask design,
The fabrication is almost identical to that of the SG / SSG DBR laser, but the faceted AR coating is not needed when the grating is designed for high peak reflectivity. Alternatively, a light-absorbing region that cuts off all unwanted reflections from the facet can be used.

Although there may be some radiation loss associated with the power splitter of the Y-type laser, it is unlikely that it will be higher than the radiation loss of the tunable coupler section of the GCSR.

[Brief description of the drawings]

FIG. 1 is a vertical cross section of an SG-DBR laser. Unlike a conventional DBR laser, the reflector is formed by two gratings that are periodically modulated (sampled) with different sampling periods.

FIG. 2 is a schematic diagram of a GCSR laser structure.

FIG. 3 is a top view (schematic diagram) of the proposed “Y-SSG” laser.

FIG. 4 is a schematic view of a ring resonator (S) SG laser.

FIG. 5 is a transmission characteristic of a ring resonator.

FIG. 6 is a principle scheme of a laser according to the present invention,
It comprises one active element and a plurality of active sections which are either transmission filters or reflectors.

FIG. 7 is a principle scheme of a prior art laser, comprising one active element and a plurality of reflectors, said active element bordering on said plurality of reflectors.

FIG. 8 is a principle scheme of the second embodiment of the present invention, which includes one active element and a plurality of sections connected in parallel with each other.

FIG. 9 is a principle scheme of the fourth embodiment of the present invention, which includes one active element and a cascade of transmission filters whose ends are reflectors.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Laser light, 20 ... Amplification effect, 30 ... Active element, 40,60,70,80 ... Connection, 50 ... Transmission filter, 90,100,110,320,330 ... Reflector, 120 ... Section, 130,140 ... spacing, 150 ... transmission properties, 160 ... reflection properties, 200, 450, 730 ... power splitter, 300 ... active section with two sides, 310 ... light beam, 340 ... laser properties, 350 ... gain curve, 360 ... tuning Range, 370 ... center frequency, 410, 420, 430, 440, 630, 710, 7
20, 930: reflector, 500: front reflector, 510: rear reflector, 530, 600, 830: active section 540, 620: phase section, 610: coupler section, 700, 900: active area, 740, 750 ... Phase control section, 800: ring resonator, 810: (S) SG-reflector, 820: anti-reflection coating, 910, 920: filter, 940: transmission filter.

 ────────────────────────────────────────────────── ─── Continued on the front page (71) Applicant 500223486 Lakesuni Fergeit Gent Rijksuniversiteit Gent Belgium Gent 9000, Sint-Peters Nieustrat 25 (72) Inventor Hert Salet Belgium 8000 Bruges, Zwarte Rate Worth Strat No. 28/2 (72) Inventor Jens Views B.N. 7.3 Ezette, Northamptonshire, Gayton, Baker Street, 6, Gayton Photonics (72) Inventor Rule Bates Belgium 9800 Dainze, Hazenpark No. 11

Claims (19)

[Claims] 1. A semiconductor device comprising: a substrate made of a semiconductor material; and a plurality of sections on the substrate (120), all of the sections being connected to each other, at least two of the sections being resonators, and The apparatus includes a waveguide system and has a plurality of resonance maxima spaced apart from each other that provide a maximum resonance at an associated wavelength, wherein at least two of the resonance maxima of each section are essentially equally spaced. An apparatus wherein the resonance maxima of at least one of each of the two sections of the resonator overlap each other. 2. The apparatus of claim 1, wherein only one of said resonance maxima of each of said plurality of sections that are resonators overlap each other. 3. The resonator according to claim 1, wherein said resonator has a plurality of spaced transmission maxima (130) as resonance maxima, providing a maximum transmission at an associated wavelength, and an associated wavelength. A plurality of reflection maxima spaced apart from each other to provide a maximum reflection at (140)
(90), (10) having
The device according to claim 1, wherein the device is any one of (0) and (110). 4. The apparatus further comprising a two-sided active radiation generating section (30) on the substrate, wherein the plurality of sections are connected to one side of the two-sided active section. Apparatus according to claim. 5. The apparatus of any preceding claim, wherein at least one of said plurality of sections is inert. 6. The apparatus of any preceding claim, wherein at least one of said plurality of sections is active. 7. At least one of said waveguide systems has a periodically destroyed short-period structure including short-period stripped regions alternating with non-stripped regions. Apparatus according to any preceding claim. 8. At least one of said waveguide systems comprises: a diffraction grating having a plurality of repeating unit regions, each having a fixed length, thereby forming a modulation period; At least one parameter that determines the reflection or transmission of light of said grating that varies with its position in each of said repeating unit regions along a direction, said grating extending for at least two modulation periods Apparatus according to any of the preceding claims, wherein the apparatus comprises: 9. The method according to claim 1, wherein at least one of said waveguide systems is a ring resonator (800).
An apparatus according to any of the claims. 10. The active section of claim 6, wherein the active section generates a light beam by spontaneous emission over a bandwidth around one center frequency, guides the light beam, and has an optical amplification effect. Apparatus according to any of the preceding claims. 11. The combination of the plurality of sections has a combined action of a reflecting action and the light amplifying action of the active section that generates laser light at at least one of the reflected wavelengths of the combination. An apparatus according to claim 10. 12. The method according to claim 6, further comprising a plurality of power splitters for connecting some of said plurality of sections and for connecting to said active section. apparatus. 13. The apparatus according to claim 1, wherein the device comprises:
0) and a plurality of the above sections (910), (920),
Apparatus according to claims 6 to 12, which is a cascade connection with (930). 14. The connection of said active section (400) comprises a parallel connection of a plurality of sections (410), (420), (430) to another multiport side of said power splitter. Apparatus according to claim 12, which is implemented on one single port side of (450). 15. The apparatus of any preceding claim, further comprising a plurality of phase sections used to adjust the phase of the reciprocating cavity. 16. The method of any preceding claim, further comprising means for injecting current into at least some of said sections that are resonators, thereby having said transmission or reflection characteristic shifted in wavelength. apparatus. 17. A substrate comprising a semiconductor material and a plurality of sections connected on said substrate, at least two of said sections being spaced from each other to provide maximum reflection at an associated wavelength. A method for setting a laser frequency of a device having a plurality of resonators having a resonance maximum, wherein the spacing of at least two of the reflection maximums in each section is not essentially equal. Locating the resonance maxima of the resonator such that the plurality of resonance maxima of each section of the cavity overlap one another, wherein the plurality defines the laser frequency. 18. A method for changing a laser frequency of an apparatus according to claim 1 from a first frequency to a second frequency, wherein said second frequency is a first distance from said first frequency. Having a spacing, the device comprises a substrate of semiconductor material and a plurality of sections connected on the device, at least two of the sections being spaced from one another to provide maximum reflection at an associated wavelength. A resonator having a plurality of resonance maxima, wherein at least two of the resonance maxima of each section are not substantially equal in distance, and the method comprises: Changing the position with a second distance substantially less than the first distance. 19. Use of the device according to claim 4 as an integrated / semiconductor tunable optical laser.