JPS63111688A - Multiple light emission type laser diode array - Google Patents

Abstract

PURPOSE:To enable the individual modulation of an optical output from each light-emitting spot by the modulation of voltage by a construction wherein modulating electrodes for controlling a current injected into an active layer are provided in a current block layer corresponding to each stripe. CONSTITUTION:In a multiple light emission type laser diode array, modulating electrodes 13, 14 for controlling a current injected into an active layer are provided in a current block layer 1 corresponding to each of stripes 7, 8. While a forward bias voltage impressed between an anode and a cathode commonly for each array is set to be fixed, a bias voltage is impressed on the modulating electrodes 13, 14 provided in the current block layer corresponding to each array, so as to control the thickness of a depletion layer formed between the current block layer 1 and a lower clad layer 2 correspondingly to each array. By this control, the conductance of a path of a current injected into light- emitting regions 9, 10 of each array is modulated, and thereby an optical output from each light-emitting spot is modulated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a multi-point emitting laser diode array.

[Conventional technology]

FIG. 4 is a perspective view showing an example of a conventional multi-point emitting laser diode φ array. In this figure, 1 is an n-type current blocking layer (hereinafter referred to as current blocking layer. The same applies to other symbols). , 2 is a p-type lower cladding layer, 3 is a p-type active layer, 4 is an n-type upper cladding layer, 5 is an n-type contact layer, 6 is a p-type substrate, 7 and 8 are carrier injection into the current blocking layer 1. 9.1o is a light emitting region, 12 is an anode electrode, and 15 is the light emitting region 9.
, 1o, separation grooves 16 and 1 to prevent electrical mixing of
7 are cathode electrodes of the light emitting regions 9 and 1o, respectively.

Next, the operation will be explained.

When a forward bias voltage is independently applied between the cathode electrode 16.17 and the anode electrode 12, carriers are blocked by the current blocking layer 1 and flow through the stripes 7.8, respectively, and are regenerated in the light emitting regions 9 and 10. It emits light upon bonding. In particular, when the injection current exceeds the laser oscillation threshold current, the bias voltage is fixed and the optical output can be controlled mostly by the injection current. In other words, by controlling the current flowing from the cathode electrodes 16 and 17,
The light outputs emitted from the light emitting regions 9 and 10 can be changed independently.

FIG. 5 is a diagram showing the current flowing between the cathode and the anode and the optical output at that time. Injection current II, I2
, I3 are PI, P2°P3.

[Problem that the invention seeks to solve]

Since the conventional multi-point emitting laser diode array is configured as described above, in order to modulate the optical output from each light emitting region 9.1o, the injection current of each must be controlled. Ta.

Therefore, the modulation circuit has a high input impedance.

A modulation element with high gain and fast response characteristics is required,
In particular, it is always necessary to perform impedance matching, and a multi-point light-emitting type has the disadvantage that this problem exists for the same number of light-emitting points as there are light-emitting points. This invention was made to solve the above problems, and reduces the burden on the modulation circuit by combining multiple laser diodes that can modulate the laser light output by voltage modulation. Another object of the present invention is to obtain a diode array in a multi-point emitting laser with improved modulation characteristics.

[Means for solving problems]

In the multi-point emitting laser diode array according to the present invention, a current blocking layer corresponding to each stripe is provided with a modulation electrode for controlling the current injected into the active layer.

[Effect]

In this invention, while keeping the forward bias voltage applied between the anode and the canode common to each array constant, each array is By controlling the thickness of the depletion layer that occurs between the current blocking layer and the lower cladding layer in accordance with the array, the conductance of the current path injected into the light emitting region of each array is modulated, thereby modulating the light output from each light emitting point. .

〔Example〕

FIG. 1 is a perspective view of a multi-point emitting laser diode φ array showing an embodiment of the present invention.
The same symbols as in the figure indicate the same things, 11 is a cathode electrode,
13 and 14 are modulation electrodes provided on the current blocking layer 1 corresponding to the stripes 7.8 provided on the current blocking layer 1.

Next, the operation will be explained.

The diagram schematically shows the state of the depletion layer formed at the interface between the current blocking layer 1 and the lower cladding layer 2 when a bias voltage is applied to the modulation electrodes 13 and 14 while keeping the voltage between the cathode and the anode constant. FIG.

In Figure 2, 20, 21, and 22 are reverse bias voltages V
The depletion layer front on the lower cladding layer 2 side with respect to l lV2 1V3 is shown. Depending on the position of this depletion layer front, the cross-sectional area of the current path to the active layer 3 in the wave direction changes. 23 and 24 schematically show the flow of carriers.

FIG. 3 shows the reverse bias voltage V1 in the multi-point emitting laser diode array of FIG.

■? , v3 optical outputs Pi , P2 , P3
It is a figure which shows an example of the voltage-light output characteristic which shows.

At this time, the current flowing through the modulation circuit has no direct current component, but only an alternating current component due to the capacitance change of the depletion layer, and the input impedance on the laser side is extremely high.
The impedance matching problem of the modulator circuit is greatly reduced. In other words, the modulation circuit can be modulated by voltage control with low output impedance.

Further, the forward bias voltage applied between the cathode and the anode for each array is kept constant, and the bias voltage applied to the modulation electrodes 13 and 14 for each array is modulated by a modulation circuit (not shown). The optical output from each array is modulated as shown in Figure 3,
While the horizontal axis in FIG. 5 is the injection current, there is a big difference in this invention that it is modulated by voltage.

In the above embodiment, a two-point emitting laser diode array was described, but the present invention may be applied to a multi-point emitting laser diode array.

Further, in the above embodiment, the light emitting regions 9 and 10 have the same cathode electrode 11, but in particular, the stub drive 7.8
In the current blocking layer 1 between the layers, absorption of light emitted from the light emitting points A and B occurs, and if the potential of this part fluctuates, a groove reaching the substrate 6 should be formed in this part as shown in Fig. 4, or A structure may be adopted in which the potential of this portion is stabilized by providing or wiring an electrode to the current blocking layer 1 in this portion.

〔Effect of the invention〕

As explained above, in this invention, a multi-point light-emitting laser diode array is constructed by providing a modulation electrode in the current blocking layer corresponding to each light-emitting point to control the current injected into the active layer. Therefore, there is an effect that the light output from each light emitting point can be individually modulated by voltage modulation.

[Brief explanation of the drawing]

FIG. 1 shows a multi-point emitting laser according to an embodiment of the present invention.
A perspective view of the diode array, FIG. 2 is a diagram schematically showing the state of the depletion layer generated at the interface between the current blocking layer and the lower cladding layer, and FIG. 3 is a diagram showing the optical output with respect to the reverse bias voltage according to the present invention. 4 is a perspective view of a conventional multi-point emitting laser diode array, and FIG. 5 is a diagram showing optical output with respect to conventional injection current. In the figure, 1 is a current blocking layer, 2 is a lower cladding layer,
3 is an active layer, 4 is an upper cladding layer, 5 is a contact layer, 6
is a substrate, 7 and 8 are stripes, 9.10 is a light emitting region, 1
1 is a cathode electrode, 12 is an anode electrode, and 13 and 14 are modulation electrodes. Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent Masuo Oiwa (2 others) Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] In a multi-point emitting laser diode array having a current blocking layer and a plurality of stripes inside, the current blocking layer corresponding to each stripe is provided with a modulating layer for controlling the current injected into the active layer. A multi-point emitting laser diode array characterized by the provision of electrodes.