It depends on your plan. There is a provision known as qualified joint and survivor annuity that is effective on some, but not all plans.

If that is in effect for your plan your spouse's signature will be required. If not, it won't.

Check with your summary plan description or with your plan administrator to see if this applies to your plan. If you have a website you may be able to determine this from the website since plan rules sometimes be available to you online.

Although there may be reasons why having your spouse's name alongside your own may be beneficial when taking out a loan there is no actual requirement that your spouse have anything to do with your own personal financial affairs. You, as an individual, can access credit on your own if you are creditworthy. Some creditors may want your spouse to co-sign if the loan affects both parties obviously, but as mentioned, any individual who has the ability to repay a loan on their own and has demonstrated the ability to repay previous loans can apply for credit on their own.