Optical Transmitter
An optical transmitter includes: an optical modulator; a driver integrated circuit (driver IC) that supplies a modulation electrical signal for the optical modulator; a first wiring board mounted face down by flip-chip mounting to connect the optical modulator and the driver IC; a first Peltier device configured to control a temperature of the optical modulator; and a second Peltier device configured to control a temperature of the driver IC.
1 . An optical transmitter comprising:
an optical modulator;
a driver integrated circuit (driver IC) that supplies a modulation electrical signal for the optical modulator;
a first wiring board mounted face down by flip-chip mounting to connect the optical modulator and the driver IC;
a first Peltier device configured to control a temperature of the optical modulator; and
a second Peltier device configured to control a temperature of the driver IC.
2 . The optical transmitter according to claim 1 , wherein a difference in height between an upper surface of the driver IC and an upper surface of the optical modulator is 100 μm or less, and an inclination of a bottom surface of the first wiring board relative to the upper surface of the driver IC and the upper surface of the optical modulator in a height direction is within ±3°.
3 . The optical transmitter according to claim 1 , wherein a distance between a chip of the optical modulator and the driver IC is 300 μm or more and 2 mm or less, and an RF line on the first wiring board is formed in a linear shape.
14 . The optical transmitter according to claim 1 ,
wherein a temperature of the second Peltier device is set to be lower than a temperature of the first Peltier device, and the optical modulator is made of InP,
an upper surface of the first 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.
15 . The optical transmitter according to claim 1 , wherein the temperature of the first Peltier device is set in a range of 45±10° C., and
the temperature of the second Peltier device is set in a range of 30±10° C.
16 . The optical transmitter according to claim 3 , 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, and spatial optical components required for constituting the optical modulator are mounted on the Peltier device on which the optical modulator is mounted, the spatial components comprising a lens, a fiber fixing member, and a polarization beam combiner (PBC), and
the first Peltier device and the second Peltier device are configured such that in-plane densities of an n-type semiconductor element and a p-type semiconductor element satisfy a relationship of the second Peltier device>a region mounted the chip of the optical modulator on the first Peltier device>a region mounted the spatial optical component on the first Peltier device.
17 . The optical transmitter according to claim 6 , wherein the chip of the optical modulator and the driver IC are mounted in a package with a form of a high-bandwidth coherent driver modulator, HB-CDM,
an electrode pad with a differential signal interface is formed in an electrical signal path of an input portion 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, the RF electrode pad of the RF terrace and the electrode pad of the driver IC are connected via a second wiring board, and an inclination of a bottom surface of the second wiring board relative to an upper surface of the driver IC and an upper surface of the RF electrode pad in a height direction is within ±3°.
18 . The optical transmitter according to claim 1 , wherein the driver IC and a chip of the optical modulator are mounted on a same subcarrier, and a thermal separation groove is provided on an upper surface of the subcarrier in a vicinity of at least one of sides facing each other, or provided on at least one of an upper surface or a bottom surface of the subcarrier between the driver IC and the chip of the optical modulator.