Semiconductor light emission device

[Detailed Description of the Invention]

[Summary of the Invention] The semiconductor laser in which Polarization plane of the laser beam within a laser resonator will change from TM mode from TE mode, or TM mode to TE mode if the light poured into pn junction is changed, It has a means which takes out outside the light emitted from the semiconductor laser through the light analysis child with a light analysis child who makes only a laser beam with one of Polarized wave in TE mode or TM mode penetrate, and is change of an inrush current, The mode is changed between TE mode and TM peach-, the intensity of the light taken out outside is changed, and the big lightwave pulse of an optical quenching ratio is obtained at high speed. [Industrial Application] The present invention relates to a semiconductor emission device, uses the laser from which Polarized wave changes between TE mode and TM peach- especially, and relates to the luminescent device which obtains the big lightwave pulse of an optical quenching ratio at high speed. [Description of the Prior Art] The current-optical power characteristic of having threshold 1.th of a typical semiconductor laser is shown in Drawing 8 (a). As shown in the figure (b), direct-current bias current Ib of I b / 1th =0.8~1.0 is sent through laser with such the characteristic, and optical power is modulated for abnormal-conditions current Is in piles to this. However, by this method, in order to lengthen transmission distance and to enlarge an optical quenching ratio so that clearly from the amplitude of the abnormal-conditions current of Drawing 8 (c), and the relation of the optical quenching ratio of light, abnormal-conditions current must be enlarged, and change of optical power must be enlarged. However, it carries out, and is and it is [ One's mouth or ] . to produce the large electric power abnormal-conditions machine which is needed for this reason. The stress which gives large electric power abnormal conditions to laser becomes large, and reliability falls. In order to enlarge abnormal-conditions electric power, it is necessary to use a large electric power transistor but, and since junction capacity is large, speed of response worsens and does not let a large electric power transistor pass to improvement in the speed. It becomes difficult to cut whether they are abnormal conditions, so that the laser itself becomes large amplitude. This is for cutoff frequency Fc of laser to fall, as shown in Drawing 8 (d). If amplitude modulation width of laser is enlarged, fluctuation of the carrier density in laser will arise, the single white of laser falls, and spectrum width spreads. If spectrum width becomes large since the wave of the light which follows the inside of a fiber changes with wavelengths (wavelength dispersion of a fiber), a waveform will be distorted by long-distance transmission and the product of transmission distance and modulation frequency will be restricted to a low value. Therefore, it is a spread of a spectrum, if amplitude is enlarged in order to lengthen transmission distance, Distance is restricted, if amplitude is made small in order to make a spectrum small, optical power will become small and the fault that transmission distance is restricted by the loss of a fiber will arise (see the relation between the spectrum width of ■ of Drawing 7 (a), and abnormal-conditions amplitude). By on the other hand making higher than L4 Low value 1th bias current rb shown in Drawing 8 (b), as shown in Drawing 7 (b), the frequency characteristic of the laser itself can be improved. It is although Was it which makes a spread of a spectrum small is made so that it may be ■ of Drawing 7 (a), Since it will be in a laser oscillation state also on zero level of a signal if Ib/Ith becomes larger than one as shown in Drawing 7 (e), the ratio (optical quenching ratio) of the light intensity of 0 and 1 becomes small, and there is a fault that the improvement in the speed by this method is difficult. [Problem(s) to be Solved by the Invention] In the former, in order to lengthen transmission distance and to enlarge an optical quenching ratio as mentioned above, abnormal-conditions current must be enlarged, and change of optical power must be enlarged. However, for this reason, it spreads producing a needed large electric power abnormal-conditions machine in One's mouth, and the stress which large electric power abnormal conditions give to laser becomes large, and reliability falls. The frequency characteristic deteriorated, abnormal conditions became being hard to start, or spectrum width spread, so that the laser itself became large amplitude, and there were various faults -- transmission distance becomes short. [Means for Solving the Problem] In a semiconductor laser in which Polarization plane of a laser beam within a laser resonator will change from TE mode to TE mode from TM mode or the 7M mode if the present invention changes light poured into pn junction, Shift of Polarized wave of TE and TM uses this paying attention to happening with very little current, It has a means which takes out outside light emitted from the semiconductor laser through the light analysis child with a light analysis child who makes only a laser beam with one of Polarized wave in TE mode or the 7M mode penetrate, and is change of an inrush current, A big lightwave pulse of an optical quenching ratio is obtained at high speed by changing the mode between TE mode and TM mode, and changing intensity of light taken out outside. [Function] Since Polarized wave selectivity is bad in DFB laser, it is TM to Drawing 3 (a) and (b), The size of a profit is TE so that the correlation of the oscillation wavelength of TE and the profit of laser may be shown, If it is made to become comparable to the both sides of TM, it has been reported that oscillation mode changes between TE mode TM peach- (the autumn of Showa 58). Japan Society of Applied Physics academic lecture meeting proceedings TE of DFB-DC-PBHLD besides p 992, 5 p -P-12, and the Seki classical style, 7M mode oscillation, the Institute of Electronics and Communication Engineers light in the Showa 59 fiscal year and an electric wave section national conference, and 260 Haruhiko Tabuchi etc. If it sets up slightly compared with TE near an oscillation threshold as shown in jump reference of the oscillation axial mode of DFB laser, especially Drawing 3 (C), near a threshold, it will oscillate in the 7M mode. [ the TM ] Next, if current is made to increase, in order that a profit may move to the long wavelength side, oscillation mode moves to TE mode with a certain output. It is because TE mode is located in 20~30-person long wavelength as usually shown in Drawing 3 (a) and (c) from the 7M mode. If bias current Ib is set up using such laser just before moving from the 7M mode to TE mode, the abnormal conditions between TE mode and 7M modes will be attained with slight abnormal-conditions current. Since shift of Polarized wave in ■TE mode and the 7M mode is started with very little current by taking out this modulated light to the exterior through a light analysis child who chooses only TE wave and TM wave, The abnormal conditions between TE mode and 7M modes are used with ■ light analysis child who can perform the abnormal conditions between TE mode and 7M modes with little abnormal-conditions current and whose oppression of the fall of a frequency characteristic and a spread of a spectrum is attained, Even when rb/rth is larger than one enough, a high optical quenching ratio is obtained, and high-speed optical abnormal conditions are enabled by improving the frequency characteristic of the laser by the increase in bias current Ib. [Example] In this example, the laser which shifts to TE mode in the increase in bias from the 7M mode shown in Drawing 2 is used. It is Guide to light analysis child 3 (PBS: Prism Beam Splinter) who shows the optical system of this example in Drawing 1 and to whom 1 passes only TE wave via lens 2 with the laser chip. The light which came out of PBS3 enters into the optical fiber of 6 through lens 5. 4 is a photo acceptance unit for an optical monitor. In Drawing 2, if bias is carried out to P point and it modulates by signal current (abnormal-conditions current) Is, only change Ps of TE light will enter into fiber 6. In this example, a sufficiently high optical quenching ratio is obtained by a 5-mA (peak peak) grade as Is. the present invention -- business -- To be -- TE -- the mode -- generally the laser which shift between TM modes produces has corrugation, and is seen by the laser which lost end face reflection, for example, DFB laser. The structure is shown in Drawing 4, and it has the stripe-like Mesa structure where Sod layer 21 and p-InGaAsP contact layer 22 were formed, and is embedding this by p-1nP12.n-1nP13.n-InGaAs P 14. The pitch of depth D of the corrugation formed along with guide layer 19 is 400 nm for 50~150 ns. Laser length LL is 400 micrometers. And in order to lose reflection to the end face, coating 18 of A12Q3 is almsgiving. 15 is 5i02 film and 16.17 is Electric bridge of laser. Although the example using the laser which shifts to TM mode TE mode above was shown, the laser which shows shift in the TE mode 7M mode is also seen. For example, in the characteristic of the semiconductor laser shown in Drawing 5, shift in the TE mode 7M mode is observed. The spectrum of the laser is shown in Drawing 6, and it is TE below in an oscillation threshold at I/Ith=0.8, It turns out that the spectrum which separated TM was shown, it is oscillating only in TE mode in I/Ith=1.8, and the 7M mode has appeared in the short wavelength side in TE mode in I/Ith=2.0. In the present invention, the intensity of the light which makes TE mode TM mode change cause by change of through and an inrush current, and takes out to the exterior the light analysis child who lets only Polarized wave in the 7M mode pass to the example and contrary of light can be modulated using such laser. [Effect of the Invention] As mentioned above, according to the present invention, the effect taken below is acquired. ■ Even if abnormal-conditions current Is is small, a high optical quenching ratio is obtained, a S/N ratio improves, and transmission distance is made for a long time. ■ Since the amplitude of abnormal-conditions current is small, high-speed abnormal conditions are made comparatively simply and a spread of spectrum width can also be made small, long-distance transmission is attained at a high speed. ■ Since bias current can be set as a sufficiently bigger position than rth, the frequency characteristic of laser improves and large scale-ization of communication capacity is attained by carrying out high-speed abnormal conditions.

[Brief Description of the Drawings]

Drawing 1 is a lineblock diagram of the example of the present invention, and Drawing 2 is an explanatory view of the example of the present invention of operation, The characteristic figure of the laser which uses Drawing 3 (a), (b), and (C) for the present invention, respectively, the important section sectional view of an element which uses Drawing 4 for an example, Drawing 5, the characteristic figure of the laser by which Drawing 6 shifts to TE-TM, Drawing 7 (a), (b), (c), and Drawing (a) (d) 8 ~ are characteristic figures of the conventional semiconductor emission device. The main numerals 1 ... Laser chip 2.5 ... Lens 3 ... PBS 4 ... Optical monitor 6 ... Optical fiber