Optical Transmitter

1 . An optical transmitter comprising:

an optical modulator;

a driver integrated circuit (driver IC) for supplying a modulation electrical signal for the optical modulator;

a first Peltier device for controlling a temperature of the optical modulator; and

a second Peltier device for controlling a temperature of the driver IC,

wherein the optical modulator and the driver IC are connected by a wire, and

the temperature of the second Peltier device is set to be lower than the temperature of the first Peltier device.

2 . The optical transmitter according to claim 1 , wherein a difference in height between an upper surface of the optical modulator mounted on the first Peltier device and an upper surface of the driver IC mounted on the second Peltier device is 100 μm or less.

3 . The optical transmitter according to claim 1 , wherein one side of the driver IC is mounted so as to protrude toward a chip side of the optical modulator with respect to a member immediately below the driver IC in a circuit plane,

one side of a chip of the optical modulator is mounted so as to protrude toward the driver IC side with respect to a member immediately below the chip in the circuit plane,

a gap between the one side of the driver IC and the one side of the chip of the optical modulator is 50 μm or less, and

a distance from the one side of the driver IC to an electrode pad is 50 μm or less and a distance from the one side of the chip of the optical modulator to the electrode pad is 50 μm or less.

4 . The optical transmitter according to claim 3 , wherein the member immediately below the driver IC is a metal block or a ceramic, and the member immediately below the chip is a subcarrier made of aluminum nitride (AlN).

5 . The optical transmitter according to claim 1 , wherein the temperature of the first Peltier device is set to 45±10° C., and

the temperature of the second Peltier device is set to 30±10°C.

6 . The optical transmitter according to claim 1 , wherein the optical modulator is made of InP,

at least one of an upper surface of the first Peltier device or an upper surface of the second Peltier device is made of aluminum nitride (AlN), and

a paste or a solder layer having thermal conductivity of 30 W/mK or more is provided between the first Peltier device and a chip of the optical modulator and between the second Peltier device and the driver IC.

7 . The optical transmitter according to claim 1 , wherein a spatial optical component is mounted on the first Peltier device on a side of a chip of the optical modulator opposite to the driver IC,

the first Peltier device and the second Peltier device respectively include an n-type semiconductor element and a p-type semiconductor element, and

in-plane densities of an the n-type semiconductor element and the p-type semiconductor element are set such that the in-plane density of the second Peltier device, the in-plane density of a mounting region of the chip of the optical modulator on the first Peltier device, and the in-plane density of a mounting region of the spatial optical component on the first Peltier device are in descent order.

8 . The optical transmitter according to claim 1 , wherein a chip of the optical modulator and the driver IC are mounted in a package of a high-speed driver integrated optical modulator (HB-CDM),

electrode pads with a differential signal interface are formed in an electrical signal path of each of an input unit of the package, the driver IC, and the chip of the optical modulator, and

a difference in height between an upper surface of an RF terrace on which a radio frequency (RF) electrode pad of the input unit is formed and an upper surface of the driver IC is 100 μm or less,

a gap between the RF terrace and the driver IC in a circuit plane is 100 μm or less, and

the RF electrode pad of the RF terrace and the electrode pad of the driver IC are connected by a wire.