JPH05226785A - Distributed feedback type semiconductor laser - Google Patents

Abstract

PURPOSE:To facilitate the phase matching by forming the stripes of a plurality of DFB lasers in parallel with each other on one substrate and optically and electrically connecting them in series through the wave-guiding channel of a total reflection mirror part to increase an optical output and besides control a voltage applied to a phase adjusting region. CONSTITUTION:The stripes 2a to 2f of a plurality of DFB lasers are formed in parallel with each other on a semiconductor substrate 1. And light generated from the stripe 2a is wave-guided to the next stripe 2b with a total reflection mirror part 3a (optical connection part) including a wave-guiding channel making use of total reflection, and the total reflection mirrors 3a to 3e are staggered with every two stripes so that the light generated from the stripe 2b is wave- guided to the stripe 2c by the total reflection mirror part 3b. The phase adjusting regions 4a to 4j for matching the phase of diffraction grating of generated light are formed between the respective stripes 2a to 2f and the total reflection mirror parts 3a to 3e.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a distributed feedback semiconductor laser (DF) used for optical communication, optical measurement, optical fiber sensor and the like.
B laser).

[0002]

2. Description of the Related Art At present, in the field of optical communication and the like, Fabry-Perot cavity type semiconductor lasers, surface-emitting type lasers, DFB lasers, distributed reflections are used as semiconductor lasers centering on the minimum loss wavelength band of 1.55 μm. Type laser diode (Di
stributed Bragg Reflector Semiconductor Lasers-D
BR laser) and the like are used.

[0003]

By the way, 1.55μ
Since it has chromatic dispersion in the wavelength band of m, when the above Fabry-Perot cavity type semiconductor laser that oscillates in multimode during high-speed direct modulation is used as a light source, the light output is strong, but the spectrum is temporal and temporal. The oscillation wavelength band is wide, and the transmission band is significantly limited.

On the other hand, DFB lasers, DBR lasers, surface-emitting lasers and the like which use a diffraction grating having wavelength selectivity as a resonator reflector have a narrow oscillation wavelength band, but have a weak optical output. Therefore, there is a demand for a semiconductor laser whose oscillation spectrum does not spread even during high-speed direct modulation.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a DFB laser having a high optical output.

[0006]

In order to achieve the above-mentioned object, the present invention has a plurality of DFB laser stripes formed in parallel on a semiconductor substrate, and each stripe is optically connected and electrically connected. A total reflection mirror portion formed of a waveguide formed so as to be connected in series with each other, and a phase adjustment region formed between the end portion of each stripe and the total reflection mirror portion to match the phase of each stripe. It is characterized by

[0007]

The stripes of the DFB laser in which a plurality of them are formed in parallel are optically connected via the total reflection mirror section,
In addition, since they are connected so as to be electrically connected in series, the length of the stripe is substantially lengthened and the light output is increased.

[0008]

Embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, a plurality of (6 in the embodiment) DFB laser stripes 2a to 2f are formed in parallel on a semiconductor substrate 1 (stripe 2a is an optical input stripe and stripe 2f is an optical output stripe. And). Then, the light oscillated from the stripe 2a is guided to the adjacent stripe 2b by the total reflection mirror portion 3a (optical connection portion) which is a waveguide using total reflection, and this stripe 2
The light of b is guided to the stripe 2c by the total reflection mirror portion 3b, and total reflection mirror portions 3a to 3e are formed in a zigzag pattern with respect to the two stripes.

Further, between the stripes 2a to 2f and the total reflection mirror portions 3a to 3e, there are formed phase adjusting regions 4a to 4j for matching the phase of the diffraction grating of the oscillated light. This requires that the phases of the diffraction gratings of the stripes 2a to 2f be matched, but if the waveguide layers are directly connected, the phases of all the stripes must be matched depending on the length of the waveguide layer. Since the control accuracy of the length is required and the manufacturing top view becomes inconvenient, it is easy to form the phase adjustment region adopted in the wavelength tunable 3-electrode DBR laser and control the voltage applied to this region. The phase is adjusted.

Thus, the total reflection mirror portions 3a to 3e described above are used.
In order to prevent a phase difference due to the polarized component, the phase difference compensating film 5 is formed by vacuum vapor deposition or the like, and the antireflection film 6 is coated on the optical connecting portion. For example, 3
Regarding the retardation compensation film 5 of the 0 ° incidence type total reflection mirror part, a dielectric film (eg, ZrO ₂ ) having a refractive index of 1.98.
When the film is formed by a method such as a sputter deposition method or a CVD method, which has a good wraparound method, the phase difference due to the polarization component can be suppressed within 1 °. The antireflection film 6 has a reflectance of 0.1% by forming the dielectric multilayer film of TiO ₂ and SiO ₂ in this order by an optical film thickness of ¼ of the laser oscillation wavelength. It can be suppressed to 1% or less.

In the above DFB laser, a plurality of (six) stripes 2a to 2f are formed in parallel and are connected in series optically and electrically by total reflection mirror portions 3a to 3e, so that they are substantially connected. The waveguide length of the DFB laser becomes longer,
It is possible to increase the light output.

The above-mentioned DFB laser has phase adjustment regions 4a ...
By utilizing the fact that light disappears when a voltage is applied to 4j and the phase is shifted by 180 °, the laser light is changed by changing the voltage (current) only in the phase adjustment region without changing the current applied to the DFB laser. It is also possible to switch the output.

Next, a method for manufacturing the above DFB laser will be briefly described. n or P type I on n or P type InP substrate
An nP buffer layer is grown, a diffraction grating of a DFB laser is patterned on the surface of the n or P type buffer layer by an interference exposure method or an electron beam exposure method, and a cladding layer (n type InP) and a waveguide layer ( InGaAsP), active layer (InGaAsP), cladding layer (P-type InP) and gap layer (InGaAs or InGaAsP)
Are grown and mesa etching is performed to form a laser waveguide (stripe) and a phase adjustment region.

Next, a block layer is grown in order of P-type InP and n-type InP, and a part of the block layer of the DFB laser in one substrate is etched to expose the n-type buffer layer and at the same time, a total reflection mirror. To form a part. Then, the insulating film and the phase compensation film are covered by a sputtering method or a CVD method, and patterned into an appropriate shape by photolithography / etching. Finally, the electrodes are formed.

In this embodiment, InP (InGaAs
The P) -based compound semiconductor laser has been described.
It can also be applied to an As-based compound semiconductor laser.

[0016]

According to the present invention, since a plurality of DFB laser stripes are formed in parallel on one substrate and are optically and electrically connected in series by the waveguide of the total reflection mirror portion, the DFB laser is practically used. The waveguide (stripe) length of the laser becomes long, and the optical output can be increased. Further, since the stripes of the DFB laser are electrically connected in series, the current flowing in one substrate is almost the same as the current flowing in one DFB laser, and the decrease in laser output due to heat generation due to the current is small. Further, by controlling the voltage applied to the phase adjustment region, it is possible to easily match the phase with the other DFB laser stripes in one substrate.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a total reflection mirror unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 2a-2f Stripe (waveguide) of DFB laser 3a-3e Total reflection mirror part (optical connection) 4a-4j Phase adjustment area 5 Phase difference compensation film 6 Antireflection film

Claims (1)

[Claims] 1. A semiconductor substrate comprising a plurality of stripes of distributed feedback semiconductor lasers formed in parallel and a waveguide formed so that the stripes are optically connected and electrically connected in series. Total reflection mirror portion, formed between the end of each stripe and the total reflection mirror portion,
A distributed feedback semiconductor laser, comprising: a phase adjustment region that matches the phase of each stripe.