0 02 micron are expitaxially grown on p type inp substrate 1 and then a sio 2 etching mask 9 is produced the interval between stripes of etching mask 9 is 2400 angstroms thereafter as shown in fig4 b absorption layer 5 is etched using the etching mask 9 as a mask subsequently as shown in fig4 c an n type in 0 72 ga 0 28 as 0 6 p 0 4 refractive index matching layer 8 is selectively grown by mocvd the thickness of refractive index matching layer 8 is 0 36 micron when the layer thickness and composition of the other layers are the same as in the above described embodiments whereby the refractive index is matched lastly the etching masks 9 are removed and as shown in fig4 d an n type inp cladding layer 7 having a thickness of 1 micron is grown thereby completing a semiconductor laser device fig2 is a cross sectional view showing a semiconductor laser device according to another embodiment of the present invention in fig2 the same reference numerals designate the same or corresponding elements as those shown in the embodiment of fig1 this embodiment operates on the basis of the same principle as in fig1 in this embodiment the refractive indices and the thicknesses of respective layers are established so that the equivalent refractive index along line c c 39 and that along line d d 39 in fig2 are equal to each other the production method of a semiconductor laser device shown in fig2 is illustrated with reference to fig5 in fig5 the same reference numerals.