Polarization sensitive optical coherence tomography using multiple polarization sensitive semiconductor optical amplifiers
This disclosure relates to an OCT apparatus configured to generate to electromagnetic (e.g., optical) signals having two different polarization states. Two or more silicon optical amplifiers (SOAs) can be configured to maintain a respective polarization state in an optical input signal provided from a light source (e.g., a broadband light source). The different polarization states can be combined by an optical combiner (e.g., a polarization maintaining fiber coupler) and provided to drive a reference arm and a sample arm implemented in an OCT system.
1. An optical coherence tomography (OCT) apparatus, comprising:
a light source configured to provide broadband light;
a first polarization sensitive semiconductor optical amplifier (PS-SOA) to receive a portion of the broadband light and to output a first polarized optical signal having a first polarization state; and
a second PS-SOA to receive another portion of the broadband light and to output a second polarized optical signal having a second polarization state, the first and second polarization states being different.
2. The apparatus of claim 1 , further comprising a splitter coupled between the light source and each of the first PS-SOA and the second PS-SOA, the splitter providing respective portions of the broadband light to each of the first PS-SOA and the second PS-SOA.
3. The apparatus of claim 2 , wherein the light source further comprises an intracavity filter configured to tune the broadband light and provide the broadband light to the splitter with a corresponding polarization state.
4. The apparatus of claim 1 , further comprising a delay line between the light source and at least one of the PS-SOAs configured to delay a respective portion of the broadband light provided to one of the first PS-SOA and the second PS-SOA relative to the broadband light provided to the other of the first PS-SOA and the second PS-SOA, such that the broadband light provided to the first and second PSSOAs have a predetermined relative phase shift.
5. The apparatus of claim 4 , further comprising a combiner configured to combine the first polarized optical signal and the second polarized optical signal to provide an aggregate polarized optical signal having the first and second polarization states and the relative phase shift.
6. An OCT system comprising:
the apparatus of claim 5 ;
an optical beam splitter/combiner configured to receive the aggregate polarized optical signal and provide a portion of the aggregate polarized optical signal to a reference arm and another portion of the aggregate polarized optical signal to a sample arm;
an optical detector to receive signals from each of the reference arm and the sample arm and to provide a detector signal based on reflected signals in each of the reference arm and the sample arm; and
a processor programmed to calculate at least one optical property for a sample associated with the sample arm based on the detector signal.
7. The OCT system of claim 6 , wherein the at least one optical property includes at least two of total reflected power, diattenuation, depolarization, birefringence, net retardance and net fast axis or extinction ratio.
8. The apparatus of claim 1 , further comprising a controller coupled to control each of the first PS-SOA and the second PS-SOA as to generate the first and second polarized optical signals with the different polarization states and out phase with respect to one another.
9. The apparatus of claim 1 , wherein the light source further comprises:
a first intracavity filter configured to tune the broadband light and provide the broadband light having the first polarization state to the first PS-SOA; and
a second intracavity filter configured to tune the broadband light and provide the broadband light having the second polarization state to the second PSSOA.
10. The apparatus of claim 9 , further comprising:
a first phase modulator configured to drive the first intracavity filter to control the first polarization state of the broadband light; and
a second phase modulator configured to drive the second intracavity filter to control the second polarization state of the broadband light.
11. The apparatus of claim 1 , wherein the light source comprises a swept laser source that includes an optical ring cavity that includes at least one optical isolator to control a direction of light propagation in the optical ring cavity.
12. The apparatus of claim 1 , wherein the first and second polarization states are maintained with a predetermined relationship in the absence of a polarization modulator.
13. The apparatus of claim 1 , wherein the first and second polarization states exhibit linear polarization that are less than or equal to about 90 degrees apart.
14. The apparatus of claim 1 , further comprising a respective polarization controller configured between the light source and each PS-SOA to help optimize a signal spectrum and balance power that is provided to each PS-SOA.
15. The apparatus of claim 14 , further comprising another polarization controller configured between each PS-SOA and a combiner.
16. A method of implementing polarization sensitive optical coherence tomography, comprising:
providing a broadband light signal;
amplifying a first polarization state for a first portion of the broadband light using a first polarization sensitive semiconductor optical amplifier to output a first polarized optical signal having the first polarization state; and
amplifying a second polarization state for a second portion of the broadband light using another polarization sensitive optical amplifier to output a second polarized optical signal having a second polarization state, the first and second polarization states being different.
17. The method of claim 16 , further comprising:
controlling polarization of the first portion of the broadband light signal that is provided to the first polarization sensitive semiconductor optical amplifier; and
controlling polarization of the second portion of the broadband light signal that is provided to the another polarization sensitive optical amplifier.
18. The method of claim 17 , further comprising:
controlling polarization of the first polarized optical signal having the first polarization state; and
controlling polarization of the second polarized optical signal having the second polarization state.
19. A system for implementing polarization sensitive optical coherence tomography, comprising:
a light apparatus comprising:
a light source configured to provide broadband light;
a first polarization sensitive semiconductor optical amplifier (PSSOA) to receive a portion of the broadband light and to output a first polarized optical signal having a first polarization state; and
a second PS-SOA to receive another portion of the broadband light and to output a second polarized optical signal having a second polarization state, the first and second polarization states being different;
an optical combiner to combine the first and second polarized optical signals to provide an aggregate polarized optical signal;
an optical splitter configured to receive the aggregate polarized optical signal and provide a portion of the aggregate polarized optical signal to a reference arm and another portion of the aggregate polarized optical signal to a sample arm;
an optical detector to receive signals from each of the reference arm and the sample arm and to provide at least one detector signal based on reflected signals from the reference arm and the sample arm; and
a processor programmed to calculate at least one optical property for a sample associated with the sample arm based on the at least one detector signal.
20. The system of claim 19 , wherein the light apparatus further comprises:
a delay line between the light source and one of the first and second PSSOAs; and
at least one polarization controller between the light source and each of the first and second PS-SOAs.