IEEE JOURNAL zyxwvutsrqponmlkji OF QUANTUM ELECTRONICS, VOL. QE-23, NO. zyxwvutsrqpo 6, JUNE zyxwvutsrq 1987 869 Monolithically-Integrated Hybrid Heterostructure Diode Laser with Dielectric-Film Waveguide DBR ZH. I. ALFEROV, S. A. GUREVICH, S. YU. KARPOV, E. L. PORTNOI, AND F. N. TIMOFEEV Abstract-In the monolithically-integrated hybrid (MIH) DBR diode laser, the five-layer Ga(A1)As-GaAs heterostructure waveguide of the gain region was monolithically butt-joined on a common GaAs sub- strate with a highly-transparent corrugated dielectric-film waveguide consisting of sputtered Si02, Ta,O,, and evaporated (corrugated) As& layers. The laser operated with the first-order grating under the pulsed current pumping at 300 K. The efficient resonant mode conversion (70 percent in power) has been obtained at the interface between the het- erostructure and dielectric waveguides. The fundamental transverse and single-longitudinal mode output emission was obtained up to 160 mW (Ich = 120 mA) with external differential quantum efficiency zyxwvut 7 = 32 percent. The advantages of a dielectric-film waveguide DBR are demon- strated. The use of such a DBR results in a high degree of sidemode suppression and stability of the spectral position of the emission Line under the temperature variation, the corresponding spectral shift being zyxwvut s 0.01 A/K. S I. INTRODUCTION EMICONDUCTOR lasers with stable monomode characteristics are in great demand for the application to fiber communications and integrated optical systems as well as to fiber-optic sensors. These lasers would be very useful as the instruments in physical experiments as well. Distributed feedback (DFB) and distributed Bragg reflec- tor (DBR) heterostructure lasers are superior to conven- tional Fabry-Perot lasers in spectral purity and modal sta- bility. A number of DFB and DBR diode laser structures with corrugated heterostructure waveguides have been suggested and tested [1]-[5]. Recently, there have been many efforts to achieve low threshold current [6], high external differential quantum efficiency [7] and adequate sidemode suppression [8] in this kind of laser. To design the perfect DBR heterostructure laser, a few conditionsshould be satisfied.Primarily,thefirst-order grating is desirable in the DBR region to avoid the con- siderable grating-coupled radiation loss [9], [ 101. Also, low-attenuation waveguides with highly regular film thicknesses must be used in DBR's [ll], [12]. However, in practice, the first-order grating is difficult to fabricate (on the surface of heterostructure waveguides) because of its small period. Another problem is that the thin-film epitaxial heterostructure waveguides are known for fail- ing to meet the requirements of low-attenuation and thick- Manuscript received October 24, 1986. The authors are with the A.F. Ioffe Physicotechnical Institute, Academy IEEE Log Number 87 1408 1. of Sciences of' the U.S.S. R., Leningrad, U.S.S.R. ness uniformity [13]. On the other hand, this is usually the characteristic for a variety of optical film waveguides, made of nonsemiconductor materials, ion-sputtered di- electric-film waveguides being the example [ 141. It should be noted that the refractive indexes of most of the dielec- tric materials used for perfect waveguides production are small in comparison with those of heterostructure wave- guides. Due to this, the period of the first-order gratings can be enlarged and its fabrication on the surface of di- electric waveguides will be simplified. Thus, the corru- gated dielectric-film waveguide can serve as an ideal Bragg mirror for the heterostructure DBR laser. To make this a practical proposition, a dielectric waveguide must be monolithically joined with a heterostructure guide on a common (heterostructure) substrate. This kind of struc- ture, consisting of monolithically-joined heterogeneous optical film waveguides shall be referred to as monolith- ically-integrated hybrid (MIH) structures. Probably, the first MIH structure was reported in [ 151. In this experiment GaAs, -.P,-GaAs and Ti : LiNb03 waveguides were monolithically butt-joined with pho- toresist and polyurethane film waveguides. The MIH structure consisting of a Ga(A1)As DH diode laser wave- guide effectively butt-joined with an AS& film wave- guide (on GaAs substrate) was demonstrated in [16]. In [17] InGaAsP-InP laser guide was connected with a polyamide film guide. In [ 181 we reported the first MIH DBR heterostructure laser. In this single-mode laser the additional advantage of the use of MIH DBR was strictly demonstrated by considerably improved temperature sta- bility of the emission line. This paper describes the recent results of investigation of Ga(A1)As MIH DBR heterostructure diode lasers op- erated at room temperature under pulsed current pumping. 11. FABRICATION OF THE MIH DBR LASERS. The MIH DBR diode laser is schematically shown in Fig. 1. This laser consists of two parts: the gain region where the Ga(A1)As heterostructure large optical cavity waveguideisusedforlightamplificationandthe DBR region in which the corrugated dielectric waveguide serves as distributed reflector. The DBR was formed on a GaAs heterostructure substrate by successive deposition of Si02 (buffer) and Ta205 films, and an additional thin As2S3 layer in which the corrugation was etched. This corruga- tion offers the periodical perturbation of the whole Si02- 0018-9197/87/0600-0869$01.00 O 1987 IEEE