VNU, JOURNAL OF SCIENCE Mathematics - Physics T XVIII, N()2 - 2002 THE IN FLU EN C E OF M A T E R IA L IN D F B L A S E R ON PARAM ETERS GENERATED IM P U LS E D in h V a n H o a n g D t'jm rtim 'ni l riiy s ic s C o llccg v o f S cicn ce - V N V Pham Van Hanh Hrimti P o ly te ch n ic In s t itu te Introduction Distributed Fmlback lasn (DFB laser) is (>IH‘ of useful light sources generating laser radiation vised widoly in optical communication his laser can generate longitudi­ nal single 1 (1«* and it* wavelength is easily modulated Especially, the DFB laser with two (or more) sortions reveals a groat, convenience to optical communication and to all o p tic a l transformation Therefore, to now this laser concentrates the attention ol many lo s r n r c h in g g r o u p s on th e w o rld a n d m a n y w orks r e la te d w ith t h i s field a r e p u b lis h e d [1-8 In this paper vvuls«* intensify I) lire transformed as seen ill Ta hip T a b le n„i AI Af I,(in a.u.) 3.0 0.11x10*5 3.3G H z 1.8x10“’ 3.4 0.12x1 (V s GHz 1.9x1 O'" 4.0 x ks 2.2H z 4.7x10'" The influrncr of IYterman coefficient Ti in cell A In this case wo have taken three values of r x (= 0.3:0.5;0.G) Repeating the analo­ gous method of calculation, till' obtained results about the change of pulse characters are presented 111 Table T a b le r, At Af I,(in a.u.) 0.3 0.15x1 (Vs 2.0G H z 0.85.x I O'" 0.5 12x 10HS 3.0G H z 1.90x10'° lOx 10 Ns 3.5G H z x ’" The influence of Peterman coefficient T in cell D We have given r *2 throe values as r = 0.1;0.2;0.3 The results, that are deduced from graphics of functions ĩ ĩ j ( t ) and Tij(üj) also display the transformation of pulse char­ acters as presented in Tttblo T a b le r At Af I, (in a.u.) 0.1 10x10 "s 3.0G H z x ’° 0.2 1 X10 Ss 0G H z 1.9x1 o'" 0.3 x1 -*s 3.0G H z 1.4x10-° Discussion and conclusions From the changes of graphics of functions 7i j ( t ) yT ij( u ) like from the values in the Tables we can reveal some interesting remarks: The augmentation of refraction index of semiconductor material in two sections results in the incroasr of pulse intensity I \ like of time interval of pulse generation A £, hut frequency r e p e t i t i o n rate A / is decreased This means that for caỗh semiconductor material of constructing DFB laser, one need choose the suitable value of refraction index in order to benefit both the frequency repetition rate as well as the pulse intensity D inh Van H oang y P ham Van H anh 24 Peterman coefficients in two sections have contrary influence on pulse characters The increase of this coefficient in section A (i.e the increase of r ị) leads to the decrease of time interval of pulse generation and the increase of pulse intensity, while the augmentation of r in section Ỉ Ì leads to the increase and decrease of corresponding quantities cited above In other words, the role of these Peterman coefficients is opposite Therefore*, choosing apprgpriate injection currents for two sections will be an important problem in the use of DFB laser with two sections in optical communication This character of Peterman coefficients is also seen in the stationary operation of DFB laser [7] It is necessary to notice that, all graphics of functions n j ( t ) } rij(u j) received hero • is deduced from parameter values given above Clearly, they don’t display stable pulses for a long time (some ten ns) This also means that used parameter values are not preferable However, tilo change of pulse characters indicated here still reveals the influence of material parameter in the use of DFB laser with two sections in all optical transformation References h : Wenzel et al., I E E E J Q E , Vol 32, 1(1996) p 69 B Sartorius et al., I E E E J Q E Vol 33, 2(1997), p 1 G Mort hier I E E E J Q E , Vol 33, 2(1997), p 231 J.D Freeze et al., I E E E J Q E , Vol 33, 8(1977), p 1253 K Otsuka et al., Phys Rev A Vol 60, 5(1999), p 3389 Siao-Lung Hwong et al., O p tics Letters,V ol 25, 9(2000), p 646 Dinh Van Hoang et al., M o d e m Problem s in O ptics a n d Spectroscopy Torn II, (2 0 ) p 406 Junichi Kinoshita., I E E E J Q E , Vol 30\ (1994), p 929 TẠP CHÍ KHOA HỌC ĐHQGHN, Tốn - Lý T.xvm, Số - 2002 ẢNH H U Ở N G C Ủ A C Á C T H A M s ố VẬT LIỆU T R O N G LA ZE DFB LÊN X U N G P H Ấ T Đinh Vùn Hoàng Khoa Vật lý, Dại học Khoa học T ự nhiên - ĐHQG Hà Nội Phạm Vân Hạnh Trường Đại học Bách Khoa Hà Nội Trong báo tim thấy ảnh hường số thamsố vật liệu hệ số Peterman» chiết xuất chất bán dản lên đặc trưng xungphát, dựa vào lời giải số theo phương pháp Runge - Kutta, hệ phương trình mỏ tả hoạt động khống dừng DFB laser ngăn ... at center of line contour and at th mode Moreover, unity in ( j i j + 1)designs t.hopresence of spontaneous omission inlaser operation The last factor in equation (3) notices the inter­ action... increase of r ị) leads to the decrease of time interval of pulse generation and the increase of pulse intensity, while the augmentation of r in section Ỉ Ì leads to the increase and decrease of corresponding... means that for caỗh semiconductor material of constructing DFB laser, one need choose the suitable value of refraction index in order to benefit both the frequency repetition rate as well as the