Transmitter optical sub-assembly (TOSA) structure and an active alignment method thereof

1. A transmitter optical sub-assembly (TOSA) structure having an independent upward heat dissipation path for dissipating heat in an upward direction; the transmitter optical sub-assembly (TOSA) structure comprising:

an independent signal source being a light source, the independent signal source comprising an LDU assembly and an optical bench assembly;

the LDU assembly comprising:

a laser diode emitting a plurality of optical signals;

a cascade LDU holding the laser diode;

a lens positioned in front of the laser diode on the cascade LDU; and

the optical bench assembly comprising:

an optical bench assembled on a photonic integrated circuit to couple light into an optical waveguide;

a plurality of passive optical components assembled on the optical bench; and wherein the laser diode and the cascade LDU are independent from the plurality of passive optical components on the photonic integrated circuit.

2. The transmitter optical sub-assembly (TOSA) structure as claimed in claim 1 , wherein the independent signal source is operably configured to actively align into an optical path for optical power coupling with the photonic integrated circuit.

3. The transmitter optical sub-assembly (TOSA) structure as claimed in claim 1 , wherein the cascade LDU is flipped with bottom side up forming a flipped cascade LDU and the flipped cascade LDU is operably configured for dissipating the heat in the upward direction.

4. The transmitter optical sub-assembly (TOSA) structure as claimed in claim 3 , wherein the flipped cascade LDU is mounted over a U-shape block.

5. The transmitter optical sub-assembly (TOSA) structure as claimed in claim 4 , wherein the U-shape block is made of a material having a lower thermal conductivity than the cascade LDU.

6. The transmitter optical sub-assembly (TOSA) structure as claimed in claim 4 , wherein the U-shape block is separated from the optical bench.

7. The transmitter optical sub-assembly (TOSA) structure as claimed in claim 4 , wherein the independent signal source further comprising the laser diode and the lens incorporated in the U-shape block and the flipped cascade LDU deposited on the U-shape block.

8. The transmitter optical sub-assembly (TOSA) structure as claimed in claim 7 , wherein the independent signal source is actively aligned to the photonic integrated circuit through the plurality of passive optical components.

9. The transmitter optical sub-assembly (TOSA) structure as claimed in claim 1 , wherein the plurality of passive optical components further comprising one or more isolators and one or more prisms.

10. The transmitter optical sub-assembly (TOSA) structure as claimed in claim 1 , wherein the cascade LDU further comprises:

a front recess on a front surface of the cascade LDU is configured with a plurality of front metal pads;

a back recess on a back surface cascade LDU is configured with a plurality of back metal pads; and

the plurality of back metal pads is electrically connected to the plurality of front metal pads through any one electrical connection selected from a vertical interconnect access electrical connection and a sidewall metal edge connection.

11. The transmitter optical sub-assembly (TOSA) structure as claimed in claim 10 , wherein the front recess of the cascade LDU is configured with an optical platform for active alignment of the lens.

12. The transmitter optical sub-assembly (TOSA) structure as claimed in claim 10 , wherein the back recess of the cascade LDU is operably configured with a wire bond platform for forming a wire bond to power up the laser diode.

13. The transmitter optical sub-assembly (TOSA) structure as claimed in claim 1 , wherein the optical assembly further comprising a transparent optical substrate with a plurality of protrusions.

14. The transmitter optical sub-assembly (TOSA) as claimed in claim 1 , wherein the independent upward heat dissipation path transfers the heat to an outer heatsink through an outer heat sink contact method without passing through the photonic integrated circuit.