TW200410465A - Phase shifted surface emitting DFB laser structures with gain or absorptive gratings - Google Patents

Abstract

A surface emitting semiconductor laser is shown having a semiconductor lasing structure having an active layer, opposed cladding layers contiguous to said active layer, a substrate, and electrodes by which current can be injected into the semiconductor lasing structure. Also included is a distributed diffraction grating having periodically alternating elements, each of the elements being characterized as being either a high gain element or a low gain element. Each of the elements has a length, the length of the high gain element and the length of the low gain element together defining a grating period, where the grating period is in the range required to produce an optical signal in the optical telecommunications signal band. A phase shifting structure is provided in the center of the grating to cause a peak intensity to occur over the center of the cavity by altering a mode profile of the output signal, while spatial hole burning arising from said altered mode profile is ameliorated.

Description

200410465 V. Description of the invention (l)

FIELD OF THE INVENTION I. The present invention relates to the field of telecommunications, and in particular to telecommunications systems based on optical signals, and more particularly to lasers, such as semiconductor diode lasers, to generate perfusion carriers. The signals are provided in this telecommunications system. Prior art ·· Rapid expansion and improvement of optical telecommunication communication systems. In this system, individual optical carrier signals are generated and adjusted to carry information. The individual signals are multiplexed together to form a dense wavelength division multiplexed (DWDM) signal. Advances in optical technology have led to closer spacing between individual signal channels. So that currently has 40 signal channels will be deployed in the c-frequency at the same time, in the near future can be configured with 80 or 160 signal channels at the same time, n r j τ policy. τ Mu same C + L frequency

Each signal channel requires an optical signal carrier source and the medium signal carrier source is usually a laser. When the number of DWDM signals is mentioned, the number of stone carrier sources should also increase. Furthermore, when the optical network pushes = 2 丄 S, the data length (data-dense long) returns to data-ligh: ^ The end user connection requires a large number of new network nodes. , V) DWDM requires multiple signal carrier sources. In the same way, we provide 1

200410465 V. Description of the invention (2) It becomes a data load function issue, because the less the data density, the closer it is to the edge of the network. A large number of different laser sources are currently allowed. These include various fixed forms of lasers with switchable or tunable wavelengths, such as Fabry-Perot, Dlstributed Bragg

Reflector, DBR), vertical cavity surface radiation laser (vcsEL), and decentralized feedback design. For example, the signal carrier usually used in telecommunication applications is the edge radiation beacon (e d g e e m i 11 i n g i n d e X) _ combined to the decentralized feedback D F B laser source. It has excellent performance in terms of modulation speed, output power, stability, tfl, and side mode suppression ratio (SMSR). In addition, communication wavelengths can be easily generated by selecting appropriate semiconductor materials and laser designs. Here S M S R means that the d F B laser characteristic has two low critical values of 100 n g i t u d i n a 1 m o d e which have different wavelengths when emitting laser light. One is desired, the other is not. The smsr includes a measure that the unwanted mode can be suppressed, and then causes more power to be transferred to the better mode. It also has the effect of reducing unwanted power emitted from another DWDM channel at this wavelength. Edge radiation]) The disadvantage of F B is that the beam pattern is stripe, which strongly migrates to two-dimensional perforations with different scattering angles due to the smaller radiation area. S ρ 〇 t c ο n v e r t e r is required to couple the signal to the signal mode fiber. This necessary technology increases costs due to difficulty and loss. Although once completed and coupled fiber can get good performance, edge emission

200410465 V. Description of the invention (3) DFB lasers have a variety of basic characteristics so that they can be fully generated, and therefore more expensive. More specifically, a large number of edge emitting D F B lasers are currently generated on a single wafer simultaneously. However, the achievable edge emission D F B laser yields (that is, those that meet the desired signal output specifications) obtained from a particular wafer can be low, based on a large number of parameters or packaging steps for the final fabrication. In particular, once formed, individual DFB lasers must be cut from the wafer. After the cutting step, the steps are completed for the terminal. Most of them are usually anti-reflective coated to one end and extremely highly reflective coated to the other end. By coating asymmetrically different ends, it helps to get good performance to one mode to cover the other ends, thus improving S M S R. However, the signal mode operation of the D F Β laser is also an equation of the phase of the fence, separated at the end of the laser cavity. Unfortunately, the phase introduced by the separate steps leads to low signal mode yields due to poor S M S R. The multi-mode laser generated in this way is not suitable for use in D W D M systems. An important feature of making edge emission D F Β lasers is that this laser can only be tested by injecting current into the laser cavity. After the laser has been completely completed, it includes cutting from the wafer and edge coating. Because of the complex model or poor S M S R, this combination of wafers has such low yields that there is no efficiency. Both surfaces of radiation and single mode operation are already available through complex coupling, by using a second or higher order grating instead of more identical first order gratings. In this second-order grating example, the resulting radiation loss is based on the fact that the laser's surface system is different for the two modes, thus enhancing degradation and causing single-mode operation. Like R. Kazarinov and C.Η.

200410465 V. Description of Invention (4)

Henry ^ MEEE, J. Quantum Electron., V o 1. Q E-2 1, p p, 144-150, Feb. 1985. With an index to the second-order grating, the spatial profile (p r o f i 1 e) of this preferred laser emission mode is bi-leaf (d u a 1-1 o b e d), which has a smaller value in the center of the laser cavity. This mode of depression is in this case a single leaf resembling a Gaussian profile with the crests in the center of the cavity. The latter mode is more conducive to most applications and is probably more critical in the field of telecommunications because it can closely conform to the appearance of a single-mode fiber and can be efficiently coupled into the fiber. This bilobal shape can only be coupled to fibers with poor efficiency. Attempts have been made in this area to transform the laser so that the mode profile can be adapted to fiber coupling, but with little success. For example, U.S. Patent No. 5970081 teaches a surface emission. Indexing the second-order grating DFB laser structure can introduce phase shift into the laser cavity by compressing the waveguide cavity structure in the middle to enhance the profile without radiation mode. And therefore coupling efficiency. However, this phase shift mode profile contains steep tips that lead to deterioration of other specifications, which is related to the promotion of space hole combustion (s p a t i a 1 h ο 1 e b u r n i n g) in the shifted region. In addition, the teachings of this invention are difficult to implant applications because of the lithography process involved. U.S. Patent No. 4,958,357 shows that a laser contains an i n d e X fusing a second-order grating to facilitate surface emission. It includes the use of a four-phase shift in the middle of the laser or a multi-phase shift within the laser cavity. This structure endures the burning of space holes as a result of extreme fields occurring in regions with phase shifts. This limits the output power of this device and is not what we would like to see.

200410465 V. Description of the invention (5) Outside the field of telecommunications, a surface emitting DFB laser structure can be referred to the US patent 5 7 2 7 0 1 3. The present invention teaches that a single leaf surface emits a DFB laser structure to generate blue / green light The second-order grating lies in the absorption layer in the structure or directly in the gain layer. This patent does not describe how grating affects fiber coupling efficiency (because it is not a concern in any communication application). This patent also does not teach what kind of parameter control is between output power and fiber coupling efficiency or how to effectively control this mode. Finally, this patent does not teach surface emitting lasers suitable for use in the communication wavelength range. Recently, attempts have been made to introduce vertical cavity surface radiation lasers, which have properties suitable for telecommunications. Such attempts have had several reasons for success. This device tends to endure manufacturing difficulties because many layer structures require as low power as very short length gain media in the cavity. This short cavity is also a source of higher noise and wider bandwidth. This wider line width limits the signal transmission distance of the signal source, because the stray failure in the optical fiber should. The chromatic dispersion effect is a problem in the telecommunications field, where different spatial components of signal pulses are transmitted through slightly different group velocities along the fiber. Therefore, pulse expansion occurs. Pulse expansion causes interference between pulses and increases bit error rate. The pulse expansion has an increase in cr 0 s s-t a 1 k between two adjacent wavelength channels. In addition, the more extra pulses pass through, the more situations there are. Therefore, the bit rate is limited by the loss of all optical connections, which is usually controlled by the fiber length and the combined pulse expansion. if

200410465 V. Description of the invention (6) The optical signal source shows a higher chirp, the pulse expansion is faster and the link length supported at a specific bit rate will be reduced. A low c h i r p source is therefore required in optical communication systems. What is needed is a surface-emitting laser structure that can provide a useful amount of output power without unfavorable space dynamic combustion problems related to the prior art phase shift design. What is needed is also a structure with a low c h i r p. SUMMARY OF THE INVENTION According to the purpose of the present invention, a surface radiation laser structure is provided, which is suitable for telecommunication applications and avoids or reduces the disadvantages of the prior art. It is yet another object of the present invention to provide a low-cost signal source capable of generating a range of signals suitable for optical bandwidth telecommunication communication signals. This signal source can be in the form of a surface-emitting semiconductor laser, which can be manufactured using traditional semiconductor manufacturing techniques and has a higher yield compared to current techniques. Another object of the present invention is to provide a low-cost advantage of generating a signal source compared to the prior art. The purpose of the present invention is to provide stable and accurate wavelength application in wideband communication applications without encountering unrealistic restrictions, based on space hole combustion. Furthermore, the present invention can be fabricated using previously counted semiconductor technologies. The invention has improved space hole combustion and provides actual value of output power generated by laser. This device shows that the minimum chirp allows signal transmission and operation without unacceptable pulse bandwidth.

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200410465 V. Description of the invention (7) The larger the number of array signal sources, the greater the demand for low error production rate. For example, producing a 40-source array with a yield of approximately 98% per source yields an array fabrication yield of only 45.5%. Each laser source of the array of the present invention can operate at the same or different wavelengths. Wavelengths within the telecommunications range are preferred. Furthermore, the device can have a built-in detection unit that connects to an external feedback path, and can use signal detection and maintenance.

According to the present invention, a surface-emitting semiconductor laser structure is provided, comprising: a semiconductor laser structure having an activation layer, a corresponding cover layer followed by the activation layer, a substrate and an electrode that can inject current into the semiconductor laser The radiation structure causes the laser structure to emit an output signal in the form of at least surface radiation; a decentralized diffraction grating is associated with the active layer of the laser structure, and the diffraction grating has a complex grating element with a large periodic transformation and A smaller gain value when the current is injected into the laser structure, the grating is normalized and shaped to generate an antimissive mode in the cavity; a phase shifting device is adapted to change the antimissive mode in the cavity to change The pattern profile is used to increase the near-field intensity of the output signal; an improved space hole combustion device is generated from the changed pattern profile. The distributed diffraction grating is a gain-coupled grating and is disposed in the activation layer. The improved space hole combustion device is derived from the changed mode profile, including

Page 12 200410465 V. Description of the invention (8) The grating element with a change has a higher gain value, and the reflection coefficient characteristic of a grating element with a higher gain decreases as more gain is provided to the grating element, where the reduction is in the reflection The coefficient of space hole combustion in the longitudinal direction is improved. The dispersed diffraction grating is a loss-coupled grating, which is adjacent to the activation layer to improve the combustion of the space cavity. The change originates from the profile of the changed mode. The grating element containing the change has a lower characteristic and has sufficient light-excitation carrier generation characteristics. As the supply gain increases, In order to compensate for the lack of carriers in the activation layer, the cavity burning in the longitudinal direction is improved. The phase shifting device includes a device for modulating the grating pitch. The modulated pitch grating is normalized and shaped across the output photon density on the laser structure. The modulated pitch grating produces a Gaussian surface radiation profile. Modulated pitch gratings cause one or more second modes to have a surface emission close to zero in the middle of the laser structure. The semiconductor mine emits a second output signal in the form of edge emission in addition to the surface emission signal. Any adjacent pair of the varying grating element having a higher gain value from the grating period to the grating element includes about 75% of the length of the grating period. The laser structure is to form a homogeneous array of N lasers to form an injection source (p u m p s 0 u r c e) with a power parameter N X N. Diffraction diffraction gratings are optically active and are formed in a gain medium in an active layer. , Wherein the dispersed diffraction grating is optically active and is formed in a loss medium in a modulus (m 0 d e v ο 1 u m e). The dispersed diffraction grating should be non-optically active and formed in a current blocking material. The dispersed diffraction grating includes an integer period of the grating on each side of the phase shift. The structure further includes an abutting region at least partially surrounding the grating in a downward direction.

Page 13 200410465 V. Description of Invention (9) The adjacent region further includes an integrated absorption region located at both ends of the distributed diffraction grating. The surface-emitting semiconductor laser structure further includes a light detector in the adjacent region. The light detector is integrated with the radiation structure. It also includes a feedback path connected to the light detector to compare the detected output signal with a preset output signal. The regulator adjusts the input current to maintain the output signal to a predetermined characteristic. The abutting region is formed from a material having electrical resistance to sufficiently electrically insulate the grating when a laser is used. The electrode contains a signal radiation opening. One of the electrodes is normalized and shaped to laterally confine the optical nuclei in the adjacent region where current is injected. In the surface emitting semiconductor laser structure, the lateral confinement electrode is a rigid body electrode (r 1 dge electrode). The array contains two or more lasers on the same substrate. The surface emitting semiconductor laser structure of the present invention, wherein every two or more of the lasers generate an output signal with a different wavelength and the output power can be individually adjusted. Every two or more of the lasers generate an output signal with the same wavelength. A method for manufacturing a surface-emitting semiconductor laser, the method comprising: forming a plurality of semiconductor laser structures by forming a continuous film layer on the same semiconductor substrate; forming a first cover layer, an activation layer, and a second cover layer on the substrate; Forming a decentralized diffraction grating and the activation layer on the substrate; forming a phase shifter in the decentralized diffraction grating with a pattern profile of a changed output signal from the semiconductor laser; forming electrodes on each of the semiconductor lasers A current has been injected on the substrate onto the radiation structure to enter the grating;

Page 14 200410465 V. Description of the Invention (ίο) Test each of the semiconductor laser structures by injecting a test current into the substrate and identically connected to the same substrate. It further includes simultaneously forming adjacent regions between a plurality of the distributed winding gratings. It further includes normalizing and shaping at least one of the electrodes in relation to the grating to laterally limit each optical mode of the semiconductor laser. It further comprises forming an absorption region in the adjacent region on each side of the grating. It further includes cutting the substrate along the adjacent area to form a laser array. Embodiment: Fig. 1 is a side view of a structure 10 of a surface emitting semiconductor laser according to the present invention. Figure 2 is an end point diagram of the same structure. The laser structure 10 includes several layers of structures using, for example, standard semiconductor fabrication techniques. The use of known semiconductor fabrication techniques in the present invention means that the present invention can be efficiently fabricated in large quantities without the need for additional new fabrication techniques. The meaning of the terms of the present invention will be known in the following. The p region of a semiconductor is doped with an electron acceptor for this region, and holes (vacancies in the valence band) are the majority of current carriers. The η region of the semiconductor is the region where the electrons are the majority current carriers. The output signal means any optical signal which is generated by the semiconductor laser of the present invention. Modulus (mode volumn) means the amount of bulk optical mode present. That is, where is there a significant signal strength, for example, the mode volumn can be the boundary enclosing of the optical mode energy

200410465 V. Description of invention (11), y. For the purpose of the present invention, a dispersed diffraction grating is a kind of light. In terms of 'active gain length' or laser a-port: absorption length of the cavity ', the feedback from the grating can cause collision or Alas, the interference of radiation effects at specific wavelengths is interference enhancement. The diffractive grating of the present invention (diffra is a lattice member, which causes the period of alternating gain sense gratings. The alternating gain effect is caused by rain adjoining the lattice member, one of which is relatively low gain. The present invention emphasizes that the phase is a positive value, and may The actual increase of the present invention emphasizes that any interference effect related to the grating pair that is different from the gain effect is sufficiently interposed at a specific wavelength. The above-mentioned alternating gain effect is established to cover the specific activation region and the carrier grating. Raster or effect. Two adjacent spacer members are set so that the difference in gain is correlated with a relatively high gain effect and the next pair of low gain effects may be small but beneficial or either absorbed or negative. Due to the absolute value of the component gain, the adjacent grating components are provided to build the laser amplifier. The invention emphasizes that any type of grating can contain loss handle and gain lightness to close the grating in the active area or not.

According to the present invention, the overall effect of a decentralized grating may be defined as limited by 1 shot collision to two 101 ^ 11 (111 ^ 丨 111〇 (1 to _, may refer to a single mode output signal. Various techniques are used to additionally design the laser so that the outline of the mode can be effectively light-coupled to the optical fiber. As shown in Figure 1, the two outer layers 12 and 14 of the laser structure 10 are electrodes. The purpose of the electrodes is to inject current Enter the laser structure i 0. It must be noted

Page 16 200410465 V. Description of the invention (12) The electrode 12 includes an opening 16 to allow the optical output signal to pass from the laser to the outside. This is described in more detail below. Although the display emphasizes the use of continuous electrodes, what is provided is the same to cause this problem. Ten: f in one section to allow the generated signal to be transmitted to the laser junction: Section J. The early metal electrode has an opening to provide a reasonable knot because it is easy to make and the cost is low. U live

A fine UP substrate or wafer 1 adjacent to the electrode 12. Adjacent to the u-wafer 17 is the buffer layer 18, which preferably includes InP. The next confinement layer 20 is formed of n-InGaAsP. This layer and the other four layers are collectively referred to as InxGal-xAsyPl-y. The third layer is collectively called Inl-xGaxAsy. The next layer is an active layer (active Uyer) 22 consisting of alternating active wells and barrier films, both of which are composed of n GaAs P or [nGaAs. Those who are familiar with this technology can know that InGaAsp or InGaAs is a better semiconductor because 11 semiconductors have been shown to have a specific composition range. The science = beneficial ability 'in a specific wavelength range is 122000nm to 170011111 or more Alas. It includes a wide-band s-frequency optical spectrum (1300_1320nm), a c-band optical spectrum (15 2 5-1 1 5 6 5 nm), and an l-frequency optical spectrum (1 5 6 8-1 6 1 0 rim). Other semiconductor materials, such as GaInNAs, InGaAlAs, can also be used as the above-mentioned film layer to provide output signal generation in the present invention.

Enter the range of broadband. In addition, the important wavelength range of telecommunications enables the device according to the present invention to be designed using appropriate materials (for example,

InGaAs / GaAs) range is 910 to 990nm, which corresponds to approximately the same wavelength range encountered. Perfusion optical amplification and fiber laser are based on Er, γb, or

Page 17 200410465 V. Description of the invention (13) Y b / E r doped material. In the embodiment of FIG. 1, the diffraction grating 24 is composed of an active layer 22. The grating 2 4 is composed of alternating high-gain portions 2 7 and low-gain portions 2 8. The preferred embodiment is that the gain 24 is a regular grating, that is, there is a uniform period through the grating, and the same size, shape, and diffusion grating in the laser as explained above. In this example, the period of the grating 24 is defined by the sum of the length 3 2 of the high gain portion 27 and the length 30 of the low gain portion 28. Comparing the low gain part 2 8 with the high gain part 2 7 shows low or no gain. For example, most or all of the activated structures in this area have been removed. According to the present invention, the grating 24 is a second-order grating, that is, the grating causes the output signal to be emitted in the form of a surface. Since the grating 24 is formed in the activation gain layer in this example, this is called a gain fit design. A phase shifter is arranged in the center of the grating 24. Contains micro-wide and high-gain “tooth” t ο 〇 t h 2 6, the size and shape of this tooth 26 is designed to shift by a quarter of a wavelength. The present invention emphasizes that any shape of the phase shifting device can also be used, as known to those skilled in the art. What is needed is to provide enough phase shift to the grating to change the near-field intensity profile to change most (primary) modes from a bimodal configuration to a unimodal configuration, where the spikes are usually above the phase shift, so the mode profile can be more Efficiency is better when compared to double impeller. Therefore, the mode profile change is provided to improve the coupling efficiency, and the characteristics of the total offset amount and the phase offset effect can be changed without departing from the spirit of the present invention.

Page 18 200410465 V. Description of the invention (14) For example, 'multi-phase offset may be used to generate a quarter wave, offset' is like two 8/8 or two 3 8/8 or other combinations. Emphasize here: such as continuous ch 1 rp grating or adjusted gap grating is also emphasized here, although it is relatively difficult to make. The adjustment gap grating of the present invention is shown in FIG. The second end-absorbing region 3 0 1 ′ is a bump electrode 3 02; the segment 304 surrounds the middle grating portion 3G3. As shown in the figure ^ Slight and located; the period of segment 304 is different. In Fig. 7, the adjustment gap can not be noticed '/, the phase shift is dispersed across the grating. Figures 8a, 8b, and 8 are theoretical diagrams of the cavity length V S cavity length for both photon density and surface radiation. The three figures (Figure 8a, Figure 8 ^, and Figure 8C) provide three basic modes. That is, the zero-order mode, — 丨 order mode, and +1 connection mode. It must be noted that from Figure 8a, it is the main one, that is, the radiation laser's zero-order mode photon density disperses the macro-span laser structure or cavity very uniformly. In fact, the peak 40 i shows less than 2.5, while the lower 40 2 is slightly less than 1. The uniform distribution of this photon reduces the problem of space hole combustion. It can be seen from Fig. 8a 'that the surface radiation profile 4 0 4 is usually round or Nans shape at 4 6. This means that the surface radiation has been tested by coupling to optical fibers in new telecommunication applications. In addition, the two second modes 8b and 8c are located in the cavity at 410 and 412, respectively, showing that the normalized near-field distribution (nie-fieid distribution) tends to zero. Such a small second mode will be coupled with the optical fiber, resulting in high-side mode suppression, when the cavity hole combustion is reduced. This group

Page 19 200410465 V. Description of invention (15) The state also has low ch i rp. In short, although many different forms of structure can be used to cause phase shift, the adjustment gap is designed to be the best form. In this article, the term “adjusting the gap design” means a grating with a slightly different period in the middle of the cavity than the end point. Even better, such periodic changes are introduced gradually across the grating. Instead of suddenly at the teeth as previously described. Referring to FIG. 1, a layer above and below the light sugar is a p-InGaAsP restriction layer 34, and a layer above the p-InGaAsP restriction layer is a p-InP buffer layer 36. On p-I η P buffer layer 3 6 is p-I n G a A s P engraved stop layer 3 8. Then, a p-InP cap layer 40 is covered by a P + + InGaAs cap layer 42. Those skilled in the art will know that semiconductor lasers with these film layers can be configured to generate output signals with predetermined wavelengths, such as distributed feedback, and write lasers into the active layer from a wound grating to cause the laser to be a single-mode laser. The correct output signal wavelength will be an equation of several variables. Variables that can be related to other laser structures can be expressed in complex forms. For example, some variables affect the output signal wavelength, including the period of the grating, the refractive index of the active layer, the limiting layer and the cover layer (usually converted into temperature as injected current), and the composition of the active range (which affects the film tension, gain wavelength, and coefficient ), And the thickness of each layer above. Another important variable is the amount of current injected into the structure through the electrodes. Therefore, according to the present invention, a laser structure with a preset output and a high specific output wavelength can be manufactured by operating these variables. Such a laser will be very useful for the application in the communication industry. Its signal source is required for individual channels or signal components that make up the DWDM spectrum. Therefore, the present invention emphasizes

Page 20 200410465 V. Description of the invention (16) The combination of film thickness, gain period, injection current, and similar parameters can produce output signals with power, wavelength, and bandwidth, which are suitable for telecommunications applications. However, it is not enough just to get the desired wavelength and bandwidth. The present invention solves the more difficult problem of generating patterns with a specific wavelength from the second-order grating (and thus surface emission), which can be controlled for effective coupling, such as to an optical fiber. The characteristics of this output signal space have a large effect on the coupling efficiency. The ideal shape is a single mode, single-leaf Gaussian. The two main modes of surface emitting semiconductor lasers include divergent two-leaf mode and single-leaf mode. The former is very difficult to couple to a single-mode fiber, which is necessary for most telecommunications applications because the fiber has a single Gaussian mode. As emphasized above, SMSR refers to the mode of suppressing unwanted in the desired mode. According to the present invention, to obtain a good SMSR operation from the surface emitting laser requires careful attention to the design of the duty cycle of the grating (d u t y c y c 1 e), and therefore the spatial gain modulation through the active layer 22. In this description, the meaning of the duty cycle means that a fraction of a grating period length has a high gain. The parameters of the duty cycle are controlled in a gain-coupled laser. As shown in Figure 1, by etching part of the activation layer and the remaining activation layer as the duty cycle, another way is that the activation gain layer can be left intact and the grating can be etched into the current blocking layer. fracti ο η corresponds to the cycle of responsibility.

Page 21 200410465 V. Description of the invention (17) In Figure 1, it can be understood that the second-order diffuse diffraction grating is an etching gain medium to form the grating 24. As a result, the two semiconductor laser fundamental modes have different radiation losses (which are the output of the laser) and therefore very different gains. Only one mode (which has the lowest gain threshold) will emit laser light, resulting in a good SMSR. The present invention emphasizes that the desired laser emission pattern is a single leaf and a roughly Gaussian profile. In this method, the laser emitting mode can be more easily coupled to the fiber because the energy profile or signal strength has the ability to couple to the fiber. There are three modes of phase-shifted second-order active coupling gratings: laser emission, two-leaf mode with higher gain criticality, and single-leaf mode with lower gain criticality. Therefore, the dominant mode is that the single-leaf contour spike lies in the phase shift position. The midpoint of the laser structure according to the present invention is optimally coupled to the optical fiber. Furthermore, according to the present invention, a device for improving space hole combustion is provided. In order to make the improved device better, the present invention emphasizes improving the performance of the laser structure beyond the limit of reducing harmfulness by burning space holes in the prior art. Those skilled in the art know that space hole combustion will not be eliminated, but only modified to allow the laser of the present invention to operate at higher output power without reducing single mode operation. It normally occurs in the phase shift design, resulting in unacceptable chr 〇ma ΐ ic dispersion or pulse broadening 〇The phase shift DBF laser has a grating related to the active layer, which is rugged (R 0 BUST according to the present invention) ) To the space hole burning, because the space hole burning device is improved

Page 22 200410465 V. Reason for Invention (18). In more detail, the present invention provides an absorbent layer having a wave-shaped activating layer or a wave-shaped activating layer related to the activating layer, for example, in a modulus (m 0 d e v ο 1 u m e). This increases the carrier injection (increasing the gain), resulting in more carriers in the high gain region, but the refractive index decreases due to the plasma effect. As a result, the coupling coefficient decreases its improved axial cavity combustion. Therefore, because the grating characteristics are related to the active layer, space hole combustion is improved. Therefore, the present invention emphasizes that the phase-shifted second-order grating is related to the active layer, which is beneficial to the phase-shift coefficient grating. When the self-inhibited space hole burning is also included as described above. Although there is no restriction on the choice of the duty cycle, if it is reasonable to operate the laser of the present invention with more energy, a duty cycle of 0.75 is believed to be better. However, other duty cycle values can also be used. From about 0.25 to 0.75 or higher. The gain duty cycle is generated at the lower grating, so self-laser can effectively increase the critical current and reduce the overall energy and efficiency. To illustrate this effect, Figure 3 depicts the characteristics of a specific two different second-order quarter-phase offset D F B lasers. One has an i n d e X coupled grating and the others are gain coupled gratings. For the purpose of making a fair comparison, it is assumed that the two lasers have the same normalization, i n d e X, the coupling coefficient K 1 L is 2 and the coupling coefficient to the radiation field is 3 / cm. In addition, it is assumed that the D F B laser gain coupling coefficient ratio is K g / K t o t a 1 with a gain of ten percent. Figure 3 therefore depicts a comparison of the field density normalized across the cavity. It can be seen that the intensity spike of the i n d e X grating is greater than the intensity spike of the gain-coupled grating.

200410465 V. Description of the invention (19) In Figure 4, the normalized gain coefficient L is the equation of the bias or injected current of the two lasers as shown in Figure 3. This provides a side mode suppression ratio annotation. It can be seen from the figure that the normalized gain difference of laser with i n d e X grating decreases rapidly with increasing bias voltage. Therefore, the quarter-wavelength structure has an i n d e X grating, space cavity combustion is a limiting factor in the high power stage, and it is a multi-mode operation source and therefore c h i r p. In contrast, the normalized gain difference of the gain laser structure of the present invention remains largely unchanged across changes in the bias current. And therefore output power. Therefore, the present invention provides a quarter-wave phase shift structure, which has a lower chirp compared to the inde X-coupled grating of the prior art. In a semiconductor laser, the multi-mode operation is a chirp source, gain or loss-coupled DFB Laser has an inherent mechanism to facilitate mode selection. Therefore, the side suppression ratio is very high, and therefore chirp is very low. More specifically, in semiconductor DFB lasers, the non-uniformity of the laser field causes non-uniform carriers to be distributed in the laser cavity because of the stimulus recombination and Hole burning. In the i n d e X light-combined laser, the lengthwise mode steadily reduces the change in the distribution of the i n d e X through refraction in the cavity. The present invention emphasizes improved space hole combustion because the gain-coupled grating is shown in the previous figure. Refer to FIG. 2 for a side view of the laser structure. As can be seen in Fig. 2, the electrodes 12 and 14 allow the application of the potential across the semiconductor structure 10 to enhance laser radiation as described above. In addition, the r i d g e portion formed by the top layer serves as a restricted optical mode.

200410465 V. Description of the invention (20) The lateral entry area is injected by current injection. When the r i d g e waveguide in this example has a strongly approximated structure, it can be fabricated using a buried he t e r o s t r u c t u r e design to limit carriers and lateral optical fields. Other forms of gain coupling design are emphasized as a means of porting the invention. For example, the replacement activation layer is as described above. As another example, a high n-doped layer can be deposited on the activation layer and a grating can be formed in this layer. This layer will not be activated in the future and therefore will not absorb or gain. Instead, it blocks charge carriers from being injected into the active layer without being etched. This structure is used for edge radiation gain coupled lasers, see C. Kazmierski, R. Robe in, D. Mathoorras i ng, A. Ougazzaden, and M. Filoche, IEEE, J. Select. Topics Quantum Electron ·, vol · 1, pp. 371-374, June, 1995. The present invention emphasizes the modification of this structure to cause surface emission and include phase shifts as described above. Referring to Fig. 5, another embodiment of a surface emitting semiconductor structure according to the present invention. In this embodiment, the electrodes 1 12 and 1 1 4 are placed on the top and bottom. The adjacent electrode 112 is an n + InP substrate 116, and then an n-InP buffer layer 118. An opening 117 is provided in the electrode 112, and a first confinement layer n-InGaAsP layer 120 is provided thereon. Above the first confinement layer 120, an activation layer 1 22 contains InGaAsP or an InGaAs quantum well layer with InGaAsP. Or the InGaAs barrier layer is separated. Then, a p-InGaAsP restricted area 124 has a p-InP buffer area 126 provided thereon. Gratings 25 are then formed as p- or n-InGaAs or

Page 25 200410465 V. Description of the Invention (21) InGaAsP absorption layer 128. A further p-InP buffer layer 130 and a subsequent P-InGaAsP etching stop layer 1 32 are formed. Then, a capping layer 1 3 4 is formed under the electrode 114 with the P + + -InGaAs capping layer 136. This embodiment presents a second (or higher) order grating in which a loss switching device is formed by providing an absorption layer and etching or similar removal. The thumb 125 includes periodic reoccurring loss or absorption elements. This grating 1 2 5 can be regarded as a light with periodic repeating high-gain elements 1 4 Q and low gain (for no Gain or loss) component 1 3 8. The composition of any high-gain element and low-gain element defines the period of the grating. The quarter-wave phase shift is provided by a phase shift tooth (t 〇 〇 t h) 1 41, which is equal to the tooth 26 in the first embodiment, and transforms the laser near-field mode. (near-fieldmodeprofile). * Figure Figure 6 shows a side view of the semiconductor laser shown in Figure 5. Current can be injected into the semiconductor laser through the electrodes 1 12 and 1 1 4 to cause radiation, as described above. \ 笔 二 ’ridge provides lateral confinement in favor of the optical field. According to the gain coupling grating of the present invention as discussed above, the loss coupling grating shown in Figure 5 & 6 also includes a device to improve the combustion of the space hole. In the following embodiments, the carrier depletion zone of the active layer is compensated by the photoexcitation (p h 〇 t 〇 e X c t e d) in the absorption layer. This has the effect of space hole burning. Furthermore, because the intensity distribution and the loss are adjusted, the present invention is more resistant to external feedback (this applies to equal gain light ^ resulting in reduced weight

Page 26 200410465 V. Description of Invention (22) Plan). As is known to those skilled in the art, this effect is not used in the previous technology inde X — c〇up 1 ed design of the JJ0 through and cavity cavity lasers against the strong field along the contrast change intensity of the near-field light display eight diagrams Before describing the description, before using the normal space peak to form a hollow cavity between the middle tip of the cavity to shoot the partial air mine, the phase, 6 and 4 are put into one, and the 4 interpretation is shown as the sixth figure of the sub-example and Figures 5 and 2 are to be repaired through holes and need to be repaired through 200 electric fields. 述 1 Scattered / graphed picture b. C. No. 2 Factorial information and diagrams. . G) stable η level ndi plus OU increase Γ rasterization of light round period into Zhoufeng peak point sharp emission projection surface to make the table can be compared with the same, a cloth eight points chart Figure 9 shows another implementation of the present invention Example top view, where the grating 150 includes finished end ports 152, 154 to improve performance. For example, the grating can be displayed on the wafer using a known technique (shown as a polyline 158), and the grating 150 can be surrounded by an adjacent area. The adjacent area 160 separates and protects the grating. Because the present invention is a surface emitting laser, rather than a split (c 1 e a v i n g) grating end emitting laser as the edge of the prior art. The present invention contemplates the need for divisional expansion in inactive adjacent areas 160. Therefore, the grating is not cut during the segmentation process, and the characteristics of each grating can be specifically designed. Preset and display writing according to semiconductor lithography operation. Therefore each grating can be fabricated with an integer number of cycles and each adjacent grating on the wafer can be displayed as the same or different from the adjacent. Gratings are limited only by the display capabilities of semiconductor fabrication technology. More importantly, unlike the previous edge emission laser ’, this grating characteristic will not change with the laser package.

Page 27 200410465 V. Description of the invention (23) Variations: The present invention emphasizes the production of grating terminal 1 5 2, 1 5 4 absorption region, which can be easily completed by non-injected current into the terminal region, as the active layer is absorbed when there is no By charge injection. In this way, this area can strongly absorb the generated optical energy and radiate in the horizontal direction. Therefore, the function of the anti-reflection layer of the prior art is realized without the need for an edge finish. In this way, the absorption region can be easily formed, for example, the film layer is built on the wafer during the semiconductor manufacturing process without any additional steps or materials. In this state, the final step (f i n i s h i n g s t e p) required by the prior art is removed, and the laser structure made according to the present invention is more cost effective than the prior art. The present invention anticipates that the segmentation passes through the adjacent region 160 away from the end point of the actual grating 150, and thus the problems derived from the prior art related to the cutting grating and therefore an uncontrollable phase shift to the cavity are thus avoided. One of the advantages of the present invention can now be understood. The present invention emphasizes a method that does not require cutting individual components from the wafer, nor does it need to complete the final or packaged laser before testing the laser function. For example, referring to FIG. 1, the electrodes 1 2 and 1 4 are formed in the substrate 10, and such a structure is established in the form of a wafer. Each structure can be electrically separated from the adjacent structure on the wafer, by appropriately patterning and depositing electrodes on the wafer, leaving a high-resistance area in the adjacent area 160 between the gratings. Therefore, the electrical characteristics of each structure can be tested on the wafer before the packaging step. Simply inject each grating structure on the current wafer, so defective structures can be removed or excluded from implementation

200410465 V. Description of the invention (24) Before the packaging step. This means that the laser structure made according to the present invention is more efficient and cheaper. Compared with the prior art, it needs to be packaged before testing, so it is more complicated and expensive. Therefore, the segmentation, packaging, and final test steps are the steps required by the front edge radiation laser technology, which is not required by the present invention. FIG. 10 shows another embodiment of the present invention, which includes a detection area 200 arranged on one side of the grating area. The detection area can be produced by integrating with the laser structure. The film in the detection area is reverse-biased as a light detector. This detector essentially emits laser light on the surface and can be easily integrated with the laser structure making it inexpensive to include. In this method, the signal output is converted into power stability, which can be detected in time. This detection can be used with external feedback paths to adjust parameters. For example, the injected current may vary with small fluctuations in output power control. Such a feedback system allows the present invention to provide a very stable output signal to adjust the required output or to compensate for changes in the environment. For example, changes in temperature and the like may cause chaos in the output signal. Changes in the output signal can therefore be compensated by changing parameters, such as current injection lasers. In this way, the present invention emphasizes a built-in detector to achieve the purpose of establishing a stable signal source, and has the required output wavelength beyond the range of conditions. FIG. 11 is a top view of an array of a semiconductor laser structure 10 of the present invention, all formed on a single identical substrate 400. In this example, each grating 24 can be designed to produce a specific output converted to a wavelength and output power. this invention

Page 29 200410465 V. Description of the invention (25) It is expected that each adjacent signal source is formed with the same wavelength or a special signal, as if each of them is at a different wavelength or a different signal. Therefore, the present invention contemplates that a single array structure whose spectrum of transmitting individual wavelengths at the same time is suitable for broadband communication from a plurality of sides, with a semiconductor laser structure. Each laser structure or single source can be independently adjusted and multiplexed into the DWDM signal. Although easy-to-understand diagrams have been shown, due to the flexibility of the design, this array can contain from two to forty or more individual wavelength signals from the same substrate 400. It can also be understood that each laser source is adjusted to the same frequency, which is coherent, and then the N laser array will have the same power constant N * N.

For those skilled in the art, although the present invention is explained above with a preferred example, it is not intended to limit the spirit of the present invention. Modifications and similar arrangements made without departing from the spirit and scope of the present invention should be included in the scope of patent applications described below. This scope should cover all similar modifications and similar structures, and should be interpreted in the broadest sense. Symbol comparison: laser structure 1 0 electrode 1 2 and 1 4 are electrodes

Openings 1 6 Substrate or wafer 1 7 Restriction layer 2 0 Active layer 22

Page 30 200410465 V. Description of the invention (26) Diffraction grating 2 4 High gain part 2 7 Low gain part 2 8 Micro wide high gain "tooth" tooth 26 Length of high gain part 3 2; Length of low gain part 3 0 Restriction layer 3 4 Buffer layer 3 6 I insect stop layer 3 8 Cover layer 4 0 Cover layer 42 End absorption region 3 0 1 Bulge electrode 3 0 2 Side end absorption segment 3 0 4 Intermediate grating portion 3 0 3 Spike 40 1 Surface radiation profile 4 0 4 Gaussian formation 4 0 6 4 1 0 and 4 1 2 The normalized near-field distribution at the center of the cavity shows zero electrode 1 1 2 and 1 1 4 Substrate 1 1 6 Buffer Layer 1 1 8 Opening hole 1 1 7 First restrictive layer 1 2 0 η Page 31 200410465 V. Description of the invention (27) Active layer 1 2 2 Restricted area 1 2 4 Buffer area 1 2 6 Grating 1 2 5 Absorptive layer 1 2 8 Buffer layer 1 3 0 Etch stop layer 1 3 2 Cover layer 134 Cover layer 1 36 Grating of high gain element 1 4 0 Low gain element 1 3 8 Phase shift tooth (t ο 〇th) 1 4 1 Phase shift forms a peak 1 4 4 Finished end portion 152, 154 Wafer 1 5 6 Grating 1 5 0 Adjacent area 1 60 Detection area 2 0 0Single identical substrate 400

Page 32 200410465 Brief description of the drawings The preferred embodiment of the present invention will be described in more detail in the following explanatory text with the following figures: Figure 1 shows the side view of the structure of the surface emitting semiconductor laser of the present invention. Figure 2 is an end point diagram of the same structure. Figure 3 depicts the characteristics of two different second-order quarter-phase-shifted DFB lasers. Figure 4 represents the normalized gain coefficient L as the equation of the two laser bias or injection currents in Figure 3. FIG. 5 is another embodiment of a surface emitting semiconductor structure according to the present invention. FIG. 6 shows a side view of the semiconductor laser of FIG. 5. FIG. 7 is a schematic diagram of an adjusted gap grating of the present invention. The eighth figure is the corresponding diagram of the optical near-field intensity versus the distance along the laser cavity in the main mode of the first embodiment of the present invention. Figures 8a, 8b, and 8c show both Theoretical plot of field density vs cavity length.

200410465

Claims (1)

200410465 6. Scope of patent application 1. A surface emitting semiconductor laser structure comprising: a semiconductor laser structure having an activation layer, a corresponding cover layer followed by the activation layer, a substrate and an electrode through which an injectable current can enter the The semiconductor laser structure causes the laser structure to emit an output signal in the form of at least surface radiation; a decentralized diffraction grating is associated with the active layer of the laser structure, and the diffraction grating has a complex grating element with a periodic conversion ratio. Large and small gain values. When the current is injected into the laser structure, the grating is normalized and shaped to generate an antimissive mode in the cavity. A phase shifting device is preferred to the antimissive mode in the cavity. The mode profile is changed to increase the near-field intensity of the output signal; an improved space hole combustion device is generated from the changed mode profile. 2. The surface emitting semiconductor laser structure according to item 1 of the scope of the patent application, wherein the dispersed diffraction grating is a gain light closing grating, which is arranged in the activation layer, and the improved space hole combustion device is derived from the changed mode profile The characteristics of the reflection coefficient including the variable grating element having a higher gain value and the higher gain grating element are reduced as more gain is provided to the grating element, wherein the reduction in the reflection coefficient improves the cavity burning in the longitudinal direction. Page 35 200410465 VI. Direction of Patent Application Scope In the long-term reform, the middle-level chemist should deserve nothing. Compensating for burning and replenishing with the same, and / or adding space to the surface, the items are said to contain 1 --- > The first enveloping device, the second one is to apply for the bias, and the other is to apply for the position. Hai = the distance between the shape and the shape of the installation. Fan Li specially requested to apply for the lose, the upper structure of the structure of the projectile laser body, the guide span 4 ^ -transverse beam surface shape table and the chemical regulations Grid light distance. Interval densification tone The light out of the fan Fan Li specially applied for the structure of the shooting light 〇 body guide wheel semi-radiation shooting surface surface appearance of the item of high-production grid light interval between the tone Fan Li specially asked to apply for the letter & u " letter firing in addition to the item of the firing laser guide. : The face number and the letter of the letter should be shot at the second lead of the mine, and the amount should be put at home and abroad. Fan Li specially requested to apply the item grid light and period of the projectile laser guide semi-radiation surface table% weekly 5 M, ^ Luminosity from the long-term period to the neighboring grid He Guangren. The enclosing value of Guangyi Dagger has become higher. Page 36 200410465 Page 37 200410465 6. Scope of patent application 1 6. The surface-emitting semiconductor laser structure according to item 15 of the scope of patent application, wherein the adjacent region further includes an integrated absorption region located at both ends of the distributed diffraction grating. 1 7. The surface-emitting semiconductor laser structure according to item 15 of the patent application scope, which further includes a light detector in the adjacent area. 18 · The surface-emitting semiconductor laser structure according to item 17 of the scope of patent application, wherein the light detector is integrated with the radiation structure. 19. The surface-emitting semiconductor laser structure according to item 17 of the scope of patent application, which further includes a feedback path connected to the light detector to compare the detected output signal with a preset output signal. 20. The surface-emitting semiconductor laser structure according to item 19 of the patent application scope further includes an adjuster to adjust the input current to maintain the output signal to a predetermined characteristic. 2 1. The surface-emitting semiconductor laser structure according to item 15 of the scope of patent application, wherein the abutting region is formed from a material having sufficient electrical resistance to electrically insulate the light source when the laser is used. 2 2. If the surface-emitting semiconductor laser structure of item 1 of the patent application scope, Page 38 200410465 6. In the scope of patent application, this electrode contains signal radiation openings. 23. The surface emitting semiconductor laser structure according to claims 1, 2 and 3, wherein one of the electrodes is normalized and shaped in a laterally confined optical mode in the adjacent region where current is injected. 2 4 · The surface emitting semiconductor laser structure according to item 23 of the patent application scope, wherein the lateral limiting electrode is a ridge electrode. 25. The surface emitting semiconductor laser structure according to item 10 of the patent application scope, wherein the array includes two or more lasers on the same substrate. 26. The surface-emitting semiconductor laser structure according to item 25 of the patent application scope, wherein every two or more of the lasers generate an output signal with a different wavelength and the output power can be individually adjusted. 2 7. The surface emitting semiconductor laser structure according to item 26 of the patent application scope, wherein every two or more of the lasers generate an output signal with the same wavelength. 2 8. A method for manufacturing a surface-emitting semiconductor laser, the method comprising: forming a plurality of semiconductor laser structures by forming a continuous film layer on the same semiconductor substrate; forming a first cover layer, an activation layer, and a second cover layer on On the substrate; forming a dispersed diffraction grating and the activation layer on the substrate; Page 39 200410465 VI. Application scope Form a phase shifter in the decentralized diffraction grating with a pattern profile of varying output signals from the semiconductor laser; form electrodes on each of the semiconductor laser structures on the substrate The injected current has entered the grating; each semiconductor laser structure has been tested. The injected test current has entered the substrate and is connected to the same substrate. 29. The method for manufacturing a surface-emitting semiconductor laser according to item 28 of the patent application scope, further comprising forming adjacent regions at the same time between the plurality of distributed winding gratings. 30. The method for making a surface-emitting semiconductor laser according to item 28 of the patent application, which further includes normalizing and shaping at least one of the electrodes, which is related to each grating to laterally limit each optical of the semiconductor laser. mode. 3 1 · The method for making a surface emitting semiconductor laser according to item 28 of the patent application scope, further comprising forming an absorption region in the adjacent region on each side of the grating. 3 2 · The method for manufacturing a surface-emitting semiconductor laser according to item 28 of the patent application scope, further comprising cutting the substrate and forming the laser array along the adjacent area. 3 3. — Surface-emitting semiconductor lasers, including Page 40 2 0410465 6. Patent application scope-A semiconductor laser structure has an active layer, the corresponding cover layer is followed by the active layer, a substrate and electrodes enter the semiconductor laser structure through its injectable current; a dispersion The diffraction grating is related to the activation layer of the laser structure. The diffraction grating has a plurality of grating elements with periodic changes. Each of the grating elements has a gain effect. Any adjacent pair of the grating elements includes an element having One has a relatively high gain effect and the other has a relatively low gain effect. The difference in gain causes the output signal to range from 910 nm to 990 nm or 12 0 nm to 1700 nm and the grating contains a phase shifter to change The output mode is contoured to have the ability to couple the output signal to an optical fiber, and to have an improved space hole combustion device. 34. The surface-emitting semiconductor laser structure according to item 33 of the scope of the patent application, wherein the dispersed diffraction grating is a gain-coupled grating, which is arranged in the activation layer, and the improved space hole combustion device is derived from the changed mode profile Including the change of the grating element has a higher gain value, and the reflection coefficient characteristic of the grating element with a higher gain decreases as more gain is provided to the grating element, wherein the reduction in the reflection coefficient improves the cavity burning in the longitudinal direction. 35. The surface-emitting semiconductor laser structure according to item 33 of the scope of patent application, wherein the distributed diffraction grating is a loss-coupled grating adjacent to the activation layer to improve the combustion of space holes. The variable grating element has a low characteristic with sufficient light-excitation carrier generation. As the supply gain increases to compensate for the lack of carriers in the active layer, the length is improved. Page 41 200410465 6. Scope of patent application Burning into the space hole. News 6 out of 3 loses the special space production limit to use the laser body to guide the semi-radiation surface type, including the first layer and a half of the cover and the cover should be covered by the frequency of the incoming signal should be sent to Dentsu, electricity injection The layer can be used in the chemical industry, and the letter is lent by a pole-transporter, a structure, and a junction plate. The base has been put into a structure. The shape of the shape and the shape of the shape are laid out by the shape of the output, and the profile is rotated by the profiler, and the structure is structured with a shooting grid. The light-to-force jet can be wound around the electricity and enter the diffused beam. The light is distributed to a number of items on the surface of the laser beam guide. 6 3 Fan Li specially requested to change the grid distance to grid. The item 7 3 of the laser beam guide surface of the laser beam should be applied in accordance with the requirements of the construction of the ΪT body. The beam of the cross-span meson light will be emitted and placed on the grid. Item 7 of the laser beam guide semi-radiation surface table Fan Li specially requested that the application of the laser beam should be based on the profile of the beam surface. The time-varying tone of the structure is the item of its laser body guide semi-radiation surface table in the structure. 7 3 Fan Li, please apply if the near-radiation surface table has the second mode or more. An intermediate-made grid structure, a light junction, and a range-to-range lightning change should be tuned to the zero Page 42 200410465 VI. Patent application scope 41. For example, the surface emitting semiconductor laser structure of item 37 in the patent application scope, wherein the dispersed diffraction grating includes a transform grating element to define a grating period, one of which is a grating element. Has a relatively high gain effect and another has a relatively low gain effect, wherein the length of the relatively high gain element is 0.75 times the length of the relatively low gain element. 42. The surface emitting semiconductor laser structure according to item 41 of the scope of patent application, wherein the dispersed diffraction grating is a gain-coupled grating in the active layer of the radiation structure. 43. The surface emitting semiconductor laser structure according to item 36 of the patent application scope, wherein the dispersed diffraction grating is a loss-coupled grating in the modulus of the radiation structure. 4 4. The surface-emitting semiconductor laser structure according to item 36 of the scope of patent application, in which the diffused diffracted light thumb is a current-carrying light that approximates the semiconductor radiation structure. Page 43